Friedberg, Jonathan W.

Introduction Limited stage disease accounts for 30-40% of Diffuse Large B-cell Lymphoma (DLBCL), with better overall survival than advanced stage disease, but with increased late relapses regardless of treatment strategy (Stephens 2016). Preferred treatment for these patients (pts) per NCCN guidelines is abbreviated R-CHOP followed by radiotherapy. Based on promising results of radioimmunotherapy consolidation in SWOG S0313 (Persky 2015), and of PET-directed experience by the BC Cancer Agency (Sehn 2011), we designed a National Clinical Trials Network (NCTN) PET-directed study to tailor therapy after 3 cycles of R-CHOP, to improve outcomes and decrease toxicities. Methods Pts had non-bulky (< 10 cm) stage I/II untreated DLBCL. Mediastinal, HIV-associated, testicular, central nervous system, and indolent lymphoma were excluded. Pts received standard R-CHOP therapy and had an interim PET scan on day 15-18 of cycle 3, which was centrally reviewed in real time. Pts with negative PET scan (Deauville 1-3, iPET-neg) proceeded with 1 additional cycle of R-CHOP. Pts with positive PET scan (Deauville 4-5, iPET-pos) initiated 36 Gy of involved field radiation therapy (IFRT), plus additional boost to FDG-avid area up to 9 Gy, within 5 weeks of 3rd cycle of R-CHOP. This was followed by ibritumomab tiuxetan (IFRT-Zevalin) 3-6 weeks after completing IFRT. Final PET scan was performed 12 weeks after treatment completion. Results The study completed accrual in June 2016. Safety, response, interim PET, and immunohistochemistry-based cell of origin (COO) and MYC/BCL2 analyses were presented previously (Persky 2017, Stephens 2017). Of 159 pts enrolled, 1 was upstaged by PET, and 26 pts were ineligible - due to incorrect histology (mostly concurrent indolent or follicular lymphoma grade 3B) (21), lack of diagnostic tissue submission for central pathology review (3), and bulky disease (2). In 132 eligible pts, median age was 62 years, 62% had stage I, 17% had B symptoms, 14% had elevated LDH, 43% had extranodal involvement, and 66% had exclusive involvement of the head and neck region. Stage modified IPI (smIPI, Miller 1998) was 0 in 27%, 1 in 42%, 2 in 28%, and 3 in 4% of the pts. COO by Lymph2Cx was assessable in 87 pts - 68% were GCB, 23% were ABC, and 9% were unclassifiable. Double protein expressers (MYC and BCL2, DPE) were 16%, while 4 (3%) pts had "double hit" lymphoma (DHL) - 2 with MYC/BCL2 and 2 with MYC/BCL6 rearrangements - none of which were DPE. Of 132 eligible pts, 128 had an interim PET scan centrally reviewed, of which 110 were iPET-neg. Only 18 were iPET-pos, 4 of them due to infection (Deauville X) which were treated as iPET-neg. Of 14 truly iPET-pos pts (11%), 2 refused radiation, and 12 pts received IFRT-Zevalin. Eight pts (67%) converted from PR to CR after IFRT-Zevalin and 4 (33%) had PR, for an overall CR of 92% and PR of 4% (with 4% unevaluable). With median follow up of 4.5 yrs (range 1.1 - 7.5 yrs), only 5 pts progressed and 2 died from lymphoma. Of 5 progressors, 3 received R-CHOP x 4, 1 was iPET-pos but declined radiation, and 1 went off treatment after 1 cycle of R-CHOP. Eleven pts died from non-lymphoma causes, including 1 pt from secondary AML (iPET-neg arm), and 1 of lung adenocarcinoma diagnosed upon iPET. S1001 5-yr PFS estimate is 87% and OS estimate is 90% (figure 1), with iPET-pos and iPET-neg pts having similar outcomes - PFS 86% vs. 88%, OS 93% vs. 91%, respectively. Five-yr PFS by smIPI was 97% for smIPI of 0, 86% for 1-2, and 30% for 3. GCB had 5-yr PFS of 95%, vs. 70% for ABC and 47% for unclassifiable. DPE pts had 5-yr PFS of 70, vs. 89% for non-DPE pts. All 4 DHL pts maintain remission. Conclusions S1001 is the largest US study of limited stage DLBCL in the rituximab era, with best NCTN results in this disease subset. Only 5 patients progressed and 2 died from lymphoma. Our study confirms the distinct biology of limited stage DLBCL, with predominance of GCB origin (68%), and head and neck location (66%). Due to small number of lymphoma events, no strong conclusions about prognostic ability of smIPI, COO, DPE, or DHL, could be made. S1001 demonstrated that 89% of pts maintained excellent outcomes after R-CHOP x 4 with PET-directed therapy. Only 11% of pts were iPET-pos and required radiation, but they also had excellent outcomes. Together with the FLYER trial in younger pts (Poeschel 2018), this NCTN trial establishes R-CHOP x 4 alone as the new standard approach to limited stage disease for majority of the pts. Disclosures Persky: Sandoz: Consultancy; Morphosys: Other: Member, Independent Data Monitoring Committee; Debiopharm: Other: Member, Independent Data Monitoring Committee; Bayer: Consultancy. Stephens:Acerta: Research Funding; Karyopharm: Research Funding; Gilead: Research Funding. Park:BMS: Consultancy, Research Funding; Rafael Pharma: Membership on an entity's Board of Directors or advisory committees; G1 Therapeutics: Consultancy; Teva: Consultancy, Research Funding; Gilead: Speakers Bureau; Seattle Genetics: Research Funding, Speakers Bureau. Bartlett:Seattle Genetics: Research Funding; ADC Therapeutics: Consultancy, Research Funding; Pfizer: Research Funding; Millenium: Research Funding; Bristol-Myers Squibb: Research Funding; Celgene: Research Funding; Genenetech: Research Funding; Immune Design: Research Funding; Gilead: Research Funding; Forty Seven: Research Funding; Janssen: Research Funding; Affimed: Research Funding; Merck: Research Funding; Pharmacyclics: Research Funding. Swinnen:Pharmacyclics: Consultancy; AbbVie: Consultancy. Barr:Celgene: Consultancy; Merck: Consultancy; Seattle Genetics: Consultancy; Genentech: Consultancy; Verastem: Consultancy; Gilead: Consultancy; Astra Zeneca: Consultancy, Research Funding; Janssen: Consultancy; AbbVie: Consultancy; Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding. Leonard:Nordic Nanovector: Consultancy; Akcea Therapeutics: Consultancy; BeiGene: Consultancy; Gilead: Consultancy; Miltenyi: Consultancy; ADC Therapeutics: Consultancy; Nordic Nanovector: Consultancy; Akcea Therapeutics: Consultancy; Sandoz: Consultancy; ADC Therapeutics: Consultancy; Miltenyi: Consultancy; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy; Karyopharm Therapeutics: Consultancy; Epizyme, Inc: Consultancy; Sutro Biopharma: Consultancy; AstraZeneca: Consultancy; AstraZeneca: Consultancy; Bayer Corporation: Consultancy; Bayer Corporation: Consultancy; Celgene: Consultancy; Epizyme, Inc: Consultancy; Celgene: Consultancy; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy; Merck: Consultancy; MorphoSys: Consultancy; Karyopharm Therapeutics: Consultancy; Gilead: Consultancy; Sutro Biopharma: Consultancy; BeiGene: Consultancy; Merck: Consultancy; MorphoSys: Consultancy; Sandoz: Consultancy. Kahl:TG Therapeutics: Consultancy; ADC Therapeutics: Consultancy, Research Funding; Seattle Genetics: Consultancy; BeiGene: Consultancy. Fisher:Celgene: Consultancy; AstraZeneca: Consultancy; Barclays: Honoraria; prIME: Honoraria. Rimsza:NanoSting: Patents & Royalties: Named inventor on a patent licensed to NanoSting [Institution]. Smith:Portola Pharmaceuticals: Research Funding. Friedberg:Bayer: Honoraria, Other: Data & Safety Monitoring Committee; Acerta: Other: Data & Safety Monitoring Committee. OffLabel Disclosure: Ibritumomab tiuxetan in diffuse large B-cell lymphoma

Introduction. The VES-13 is a simple, self-reported, function based tool originally developed to screen community-dwelling populations to identify persons age 65 years and older at risk of death and functional decline, including death in the next 12 months. The VES-13 items include patient's age, self-rated overall health status, functional limitations in physical activity, and functional disabilities in more complex activities of daily living. As part of the Lymphoma Epidemiology of Outcomes (LEO) cohort study, we collected self-reported VES-13 data at study enrollment on all participants regardless of age, and here we report on the prevalence of vulnerable status defined by the VES-13 and its association with 1-year mortality, overall, stratified at age 65 years, and in the subset of diffuse large B-cell lymphoma (DLBCL) treated with immunochemotherapy. Methods. From 7/2015 to 6/2017, 3253 participants with NHL were enrolled within 6 months of their diagnosis into the LEO cohort. 2004 were evaluable on VES-13, and 1183 (59%) completed it before the initiation of therapy. VES-13 scores range from a minimum of 0 (low risk for decline) to a maximum of 10 (greatest risk for decline), and a score ≥3 was classified as vulnerable. Clinical, pathology and treatment data were abstracted using a standard protocol, and participants were contacted every 6 months for the first three years and then annually thereafter to identify outcomes. Medical records were reviewed by LEO clinicians to classify cause of death according to a standard protocol. Therapy was determined by the treating physician, and this was independent of knowledge of the VES-13 score. The association of VES-13 with 1-year mortality from date of diagnosis was estimated using odds ratios (OR) and 95% confidence intervals (CI) from logistic regression models, which also provided model c-statistics. Results. The median age of the 2004 participants in this analysis was 62 years (range 18-94); 57% were male; 54% were ≥65 years; and 28% had a normal body mass index (BMI), 1% were underweight, 35% were overweight, and 36% were obese. Clinically, 59% of participants had an aggressive subtype, 65% were stage III-IV, 24% had B-symptoms, and 11% had a performance status (PS) of ≥2. Overall, 28% of participants were classified as vulnerable (95% CI 26%-30%), with a higher prevalence among those completing the survey after initiation of therapy (38%, 95% 34%-41%) versus before initiation of therapy (22%, 95% CI 20%-24%), and a higher prevalence for those ≥65 years (32%, 95% CI 29%-34%) versus <65 (25%, 95% CI 22%-28%). During the first year of follow-up, there were 147 deaths, with 61% due to lymphoma, 14% therapy-related, 12% due to another malignancy, 3% other causes, and 10% unknown. Significant univariate predictors of 1-year mortality included vulnerable status, older age, PS 2+, stage III-IV, aggressive subtype, lower quality of life score, lower BMI, and 1 or more comorbidities, and were included the backward stepwise modeling. Vulnerable status (OR=3.26, 95% CI 2.15-4.96) was retained in the final model that also included age, PS, stage, and NHL subtype (Table), with a model c-statistic of 0.81. As shown in the Table, these associations were similar whether VES-13 was assessed before (c-statistic 0.77) or after (c-statistic 0.81) initiation of therapy. After adjustment for age, PS, stage and NHL subtype, vulnerable status predicted 1-year mortality in participants ≥65 years (OR=1.96, 95% CI 1.15-3.36; model c-statistic 0.80) as well as <65 years (OR=6.38, 95% CI 3.07-13.3; model c-statistic 0.83). Finally, in the DLBCL patients treated with immunochemotherapy (N=521), vulnerable status (38% of patients) also predicted 1-year mortality (OR=2.11, 95% CI 1.05-4.26) after adjusting for age, PS and stage (model c-statistic 0.78). Conclusion. Based on a self-administered VES-13, 28% of newly diagnosed NHL patients in the LEO cohort were classified as vulnerable, including 25% of those <65 years, and vulnerable status was a strong predictor of 1-year-mortality, even in the subset of DLBCL patients treated with presumed curative intent. These results highlight the potential value of screening for vulnerable status overall and across a wider age spectrum in order to optimize patient management and reduce early mortality. Disclosures Martin: Karyopharm: Consultancy; Sandoz: Consultancy; I-MAB: Consultancy; Celgene: Consultancy; Janssen: Consultancy; Teneobio: Consultancy. Casulo:Gilead: Honoraria, Other: Travel, accommodation, expenses; Celgene: Research Funding; Roche: Other: Travel, accommodation, expenses. Cohen:Takeda Pharmaceuticals North America, Inc.: Research Funding; Bristol-Meyers Squibb Company: Research Funding; Hutchison: Research Funding; Astra Zeneca: Research Funding; Lymphoma Research Foundation: Research Funding; ASH: Research Funding; LAM Therapeutics: Research Funding; UNUM: Research Funding; Gilead/Kite: Consultancy; Janssen Pharmaceuticals: Consultancy; Seattle Genetics, Inc.: Consultancy, Research Funding; Genentech, Inc.: Consultancy, Research Funding. Farooq:Kite Pharma: Research Funding; Celgene: Honoraria. Friedberg:Acerta: Other: Data & Safety Monitoring Committee; Bayer: Honoraria, Other: Data & Safety Monitoring Committee. Kahl:Seattle Genetics: Consultancy; ADC Therapeutics: Consultancy, Research Funding; BeiGene: Consultancy; TG Therapeutics: Consultancy. Lossos:Janssen Scientific: Membership on an entity's Board of Directors or advisory committees; NIH: Research Funding; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees. Maurer:Nanostring: Research Funding; Celgene: Research Funding; Morphosys: Membership on an entity's Board of Directors or advisory committees. Nastoupil:Spectrum: Honoraria; Genentech, Inc.: Honoraria, Research Funding; Gilead: Honoraria; Janssen: Honoraria, Research Funding; Novartis: Honoraria; TG Therapeutics: Honoraria, Research Funding; Bayer: Honoraria; Celgene: Honoraria, Research Funding. Rutherford:Heron: Consultancy, Honoraria; Janssen Scientific Affairs: Consultancy, Honoraria; AstraZeneca: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Juno Therapeutics Inc: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria; Verastem: Consultancy, Honoraria; Karyopharm: Honoraria, Membership on an entity's Board of Directors or advisory committees. Flowers:National Cancer Institute: Research Funding; BeiGene: Consultancy, Research Funding; Eastern Cooperative Oncology Group: Research Funding; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy, Research Funding; Pharmacyclics/Janssen: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; Bayer: Consultancy; Spectrum: Consultancy; Karyopharm: Consultancy; Acerta: Research Funding; TG Therapeutics: Research Funding; Millenium/Takeda: Research Funding; AstraZeneca: Consultancy; Optimum Rx: Consultancy; V Foundation: Research Funding; Celgene: Consultancy, Research Funding; Burroughs Wellcome Fund: Research Funding; Denovo Biopharma: Consultancy; Gilead: Consultancy, Research Funding. Cerhan:NanoString: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding.

Abstract Introduction: Follicular lymphoma (FL) is the most common indolent non-Hodgkin lymphoma in the world and has a median age at diagnosis in the seventh decade. FL in young adults (YA; 40 years old or younger) is extremely rare. Currently, there are no standard approaches guiding treatment of YA patients with FL, and very little is known about disease characteristics and outcomes of YA patients with FL given limited research conducted in this vulnerable population. To gain further insight into FL in YA, we analyzed the National LymphoCare Study (NLCS) to describe disease and patient characteristics, as well as features of treatment in YA patients with FL. We previously reported that 2-year progression-free survival (PFS) is an important survival endpoint in patients with FL undergoing chemo-immunotherapy. Hence, we also sought to characterize 2-year PFS in this age group and compare it to older cohorts. Methods: Evaluablepatients were identified in the NLCS, and those between 18–40 years of age with newly diagnosed FL at any stage were classified as YA patients. Patients with mixed histology or transformed disease were excluded, as were patients with progression of disease prior to beginning first-line treatment. Survival probability was estimated by the Kaplan-Meier method. We estimated the association of age group with PFS using hazard ratios (HR) and 95% confidence intervals (CI) from multivariable Cox models. Results: A total of164 YA patients with FL were analyzed, representing 6.2% of the NLCS population, similar to the observed frequency in the Surveillance, Epidemiology, and End Results (SEER) Program data (4.8% of all FL). Sixty nine percent of YA patients had advanced stage disease. The majority of patients (80%) had low-grade histology, and 50% had good risk disease according to the Follicular Lymphoma International Prognostic Index (FLIPI). Nineteen percent of patients (31/164) underwent watchful waiting, 12% received rituximab monotherapy, and 47% received chemo-immunotherapy (61% of whom received R-CHOP [rituximab, doxorubicin, vincristine, prednisone]). There was no significant difference in FLIPI score or other baseline disease characteristics compared to adult patients aged 41–60 years. Eleven deaths occurred among YA with FL; only 5 of these were lymphoma related. Overall survival (OS) at 2 years was 97.4% (95% CI 93.3%, 99.0%), and at 5 years, 93.7% (88.3%, 96.7%), which was similar to patients aged 41–60 (97.2% [96.0%, 98.0%] at 2 years, and 92.0% [90.1%, 93.5%] at 5 years). After a median follow-up of 7.1 years, OS in YA FL was 92%. Through follow-up, there were 64 PFS events. The estimated 2-year PFS (95% CI) for YA and adults 41–60 was 75.9% (67.1%, 82.6%) and 80.9% (78.1%, 83.4%), respectively. After adjusting for FLIPI score, there was no difference in PFS for YA with FL requiring first-line treatment (excluding watchful waiting) compared to adults aged 41–60 years (HR=0.93; 95% CI 0.69, 1.25), and no difference in OS compared to adults aged 41–60 years (HR=1.19; 95% CI 0.64, 2.23). Conclusions: In the largest cohort of YA patients with FL to date, we found few differences in outcomes compared to patients aged 41–60. FLIPI and other disease characteristics were similar to adults aged 41–60 years. There were no differences between YA FL and adults aged 41–60 in PFS for all treated patients. OS in the YA group of patients with FL was outstanding. YA patients with FL have reassuringly similar outcomes to patients aged 41–60. Fertility preservation and survivorship issues should be taken into consideration when defining management strategies, but otherwise these data support that YA patients with FL should not be approached differently from older adults with the same disease. Disclosures Byrtek: Genentech, Inc.: Employment, Equity Ownership. Dawson:Genentech, Inc.: Employment, Equity Ownership. Zhou:RTI-HS: Employee of RTI-HS, which has research contracts with Genentech Other. Flowers:Seattle Genetics: Consultancy; Spectrum: Consultancy, Research Funding; Sanofi: Research Funding; Abbott: Research Funding; Novartis: Research Funding; OptumRx: Consultancy; Millennium/Takeda: Research Funding; Janssen: Research Funding; Celgene: Research Funding; Allos: Consultancy. Farber:Gilead: Speakers Bureau; Janssen/Pharmacyclics: Speakers Bureau; Seattle Genetics: Speakers Bureau; Leukemia Lymphoma Society NJ Chapter: Membership on an entity's Board of Directors or advisory committees; Genentech: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Alexion: Speakers Bureau, Stock ownership Other. Cerhan:Genentech, Inc.: LymphoCare Scientific Advisory Board Other. Link:Genentech, Inc.: Consultancy, Scientific Advisory Board for Genentech Other.

Abstract Background: Southwest Oncology Group (SWOG) S0016 was a phase III randomized study that compared safety and efficacy of cyclophosphamide, doxorubicin, vincristine, prednisone and rituximab (CHOP-R) with CHOP followed by consolidation with (131) iodine-tositumomab radioimmunotherapy (CHOP-RIT) for previously untreated follicular lymphoma (FL) patients. As reported previously, the study demonstrated excellent outcomes in both arms with 2-year progression-free survival (PFS) of 76% and 80% and 2-year overall-survival (OS) of 97% and 93% in the CHOP-R and CHOP-RIT arms, respectively. (Press. et al. JCO, 2012) We now report the long term outcome of patients who were treated on the S0016 study. Methods: Between 2001 and 2008, 531 previously untreated advanced follicular lymphoma patients were randomized to receive either 6 cycles of CHOP every 3 weeks with 6 doses of rituximab (CHOP-R) or 6 cycles of CHOP every 3 weeks followed by RIT. Patients with advanced-stage disease (bulky stage II, III or IV) with any pathologic grade (1, 2 or 3) were eligible. Results: Patients on CHOP-R (n=264) and CHOP-RIT (n=267) arms had balanced baseline characteristics including age (median 54.5 vs. 53.4 years), presence of B symptoms (29% vs. 26%), pathologic grade 3 (8% vs. 9%), "high" FLIPI risk group (22% vs. 26%), stage IV disease (59% vs. 63%), elevated β2M (53% vs. 55%), bone marrow involvement (56% vs. 55%) and bulky disease (24% vs. 26%). Objective remissions were documented in 226 of 267 eligible patients treated with CHOP-R (85%) and in 226 of 264 patients with CHOP-RIT (86%). Complete remission (CR) rate was 40% in the CHOP-R and 45% in the CHOP-RIT arm. Neutropenia was the most common adverse event (AE) in both arms (48% vs. 51%). Rate of grade 3-5 AEs were not different except for thrombocytopenia which was more common in the CHOP-RIT group (18% vs. 2%). After a median follow-up of 9.6 years (range 0.1 - 14.4 years), the estimated 10-year PFS was 42% (95% CI: 35.6%, 48.5%) in the CHOP-R arm and 57% (95% CI: 50.5%, 63.2%) in the CHOP-RIT arm (p-value = 0.01). 51% of responders on the CHOP-R arm and 38% of responders on the CHOP-RIT arm have relapsed (p-value= 0.01). The estimated 2-year relapse-free survival was 76% for CHOP-R patients and 81% for CHOP-RIT patients (p-value=0.15). There were 48 deaths in the CHOP+R arm and 59 deaths in the CHOP-RIT arm with an estimated 10-year OS of 82% (95% CI: 76.3%, 86.4%) with CHOP-R and 77% (95% CI: 70.5%, 81.4%) with CHOP-RIT (p-value = 0.18). (Figure-1) During the follow-up, 41 patients (15.4%) in the CHOP-R arm and 37 patients (14%) in the CHOP-RIT arm developed secondary malignancies. MDS/AML were more common in the CHOP-RIT arm (11 patients; 4.2%) compared to CHOP-R arm (5 patients; 1.9%) with a relative risk of 2.2 (95% CI: 0.8-6.3) (P-value 0.12). Conclusion: With almost 10 years of follow-up, patients with FL treated on protocol S0016 show outstanding survival in both CHOP-R and CHOP-RIT arms, and represent the best published long-term outcomes to date in this disease. Indeed, almost half of patients enrolled still remain progression-free, confirming registry experiences. While CHOP-RIT provided significantly longer PFS and lower relapse rate compared to CHOP-R in our study, the OS rate was not different between 2 arms due in part to higher incidence of fatal MDS/AML in the CHOP-RIT group, emphasizing the importance of long-term follow-up, and calling into question the validity of PFS as a surrogate for OS in this setting. Given these outstanding outcomes, we believe chemoimmunotherapy should remain the standard induction approach for patients with high-risk FL until long-term follow-up of alternative approaches demonstrates superiority. Support: NIH/NCI grants CA180888, CA180819, CA180821 and in part by GlaxoSmithKline Disclosures Shadman: Emergent: Research Funding; Acerta: Research Funding; Gilead: Honoraria, Research Funding; Pharmacyclics: Honoraria, Research Funding. Rimsza:NCI/NIH: Patents & Royalties: L.M. Rimsza is a co-inventor on a provisional patent, owned by the NCI of the NIH, using Nanostring technology for determining cell of origin in DLBCL.. Gopal:Paid Consultancy- Gilead, Janssen, Seattle Genetics, Spectrum, Research funding- Gilead, Janssen, Pfizer, BMS, Merck, Teva, Takeda, Spectrum, Seattle Genetics: Consultancy, Honoraria, Research Funding. Maloney:Juno Therapeutics: Research Funding; Genentech/Roche: Honoraria. Cheson:Gilead: Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta: Membership on an entity's Board of Directors or advisory committees, Research Funding. Smith:Amgen: Other: Educational lecture to sales force; TGTX: Consultancy; Celgene: Consultancy; Pharmacyclics: Consultancy; Genentech: Consultancy, Other: on a DSMB for two trials ; Portola: Consultancy; Juno: Consultancy; Gilead: Consultancy; AbbVie: Consultancy. Fisher:Seattle Genetics: Consultancy; Gilead: Consultancy; Johnson and Johnson: Consultancy. Friedberg:Bayer: Other: Data Safety Monitoring Committee. Press:Roche / Genentech: Consultancy, Research Funding.

Background: Standard first-line treatment for patients diagnosed with diffuse large B-cell lymphoma (DLBCL) is the R-CHOP regimen. Despite numerous efforts to improve on this regimen, in all comers and specifically in those with activated B-cell (ABC)-type DLBCL, results from large randomized studies have failed to show a significant clinical advantage above this standard. Recently, 2 large clinical trials in previously untreated DLBCL evaluated the combination of lenalidomide/R-CHOP (R2-CHOP) vs standard R-CHOP and demonstrated discordant results. We analyzed data from these trials to identify differences that may have impacted the disparate trial outcomes while identifying patient characteristics associated with benefit from the addition of lenalidomide across the trials. Methods: The 2 trials included in this evaluation are ROBUST, an international, randomized, double-blinded, placebo-controlled, phase III study of R2-CHOP vs placebo/R-CHOP, and the Intergroup ECOG-ACRIN 1412 (E1412) trial, a US-only, randomized, open-label, phase II study of R2-CHOP vs R-CHOP. Additional key study design differences included dosing, and subtype timing and inclusion (both studies used gene expression profiling [GEP] by NanoString). R-CHOP dosing differed only for prednisone, which was a flat 100 mg dose, d1-5 in ROBUST and 100 mg/m2, d1-5 in E1412. The lenalidomide dose and schedule varied between studies: 15 mg/d, d1-14/21 for ROBUST (210 mg/cycle) and 25 mg/d, d1-10/21 (250 mg/cycle) for E1412. ROBUST enrolled only patients prospectively identified with the ABC subtype, whereas E1412 enrolled all otherwise eligible patients and retrospectively evaluated for ABC-type with prespecified ABC-type accrual and power parameters. Both studies enrolled patients with IPI status ≥ 2, ECOG PS 0-2, and Ann Arbor stage II-IV (E1412 stage II with mass > 10 cm). The primary endpoint in both was progression-free survival (PFS; central review for ROBUST and investigator-assessed for E1412). Secondary endpoints included event-free survival (EFS; key for ROBUST), overall and complete response rates, overall survival (OS), and safety. Results: ROBUST enrolled 570 ABC patients and E1412 enrolled 280 GCB, ABC, and unclassified DLBCL patients. Patient profiles in both studies (ROBUST [ABC]/E1412 [all COO]) were similar in terms of median ages (65 y/66 y), male sex (58%/61%), and ECOG PS 1-2 (55%/63%). Patients in E1412 were more high risk: IPI 2 (42% ROBUST/34% E1412), IPI ≥ 3 (58%/66%), and Ann Arbor stage III/IV disease (87%/97%). Importantly, there was a notable difference in the time from patient diagnosis to treatment: median 31 days for ROBUST and 21 days (22% > 31 d) for E1412. Only 6% of patients in ROBUST were treated within 2 weeks of diagnosis vs 30% in E1412. At a median follow-up of ~2.5 y for both studies, E1412 met its primary endpoint of improvement in PFS with 34% reduction in the risk of PD/death (2-y PFS: 76% vs 70%) for all patients, but did not reach statistical significance in ABC-DLBCL patients for 2-y PFS (71% vs 61%) or 2-y OS (88% vs 76%). ROBUST showed no significant improvement in the primary PFS endpoint (2-y PFS: 67% vs 64%) or 2-y OS (79% vs 80%) in ABC patients. Subgroup analyses of PFS comparing R2-CHOP vs R-CHOP control within each study suggested that certain baseline factors favor the R2-CHOP arm, including: female sex, high IPI score (≥ 3), non-bulky disease (< 7 cm), and high Ann Arbor stage IV disease. Conclusion: While the ROBUST study design integrated state-of-the-art, real-time GEP to prospectively identify ABC-DLBCL patients with rapid lab turnaround time, cases of logistical delays in tissue submission for central analysis and staging procedures may have resulted in accrual of patients with lower-risk DLBCL and prolonged time from diagnosis to treatment. In contrast, E1412 retrospectively stratified patients by COO through GEP and was able to accrue higher-risk patients irrespective of COO within a shorter time from diagnosis to treatment, which among other differences (eg, smaller population size, study phase), could contribute to the improvement over R-CHOP control. Our comparative findings have significant implications for the design of future biomarker-driven trials and provide momentum for studies of novel combinations with R-CHOP in DLBCL. Further investigation into other factors, including dose intensity and their correlation with outcomes, will be presented. Disclosures Nowakowski: Celgene: Consultancy, Research Funding; NanoString: Research Funding; MorphoSys: Consultancy, Research Funding; Genentech, Inc.: Research Funding; F. Hoffmann-La Roche Ltd: Research Funding; Selvita: Membership on an entity's Board of Directors or advisory committees; Curis: Research Funding; Bayer: Consultancy, Research Funding. Chiappella:Servier: Other: advisory board, Speakers Bureau; Roche: Speakers Bureau; Teva: Speakers Bureau; Celgene: Other: advisory board, Speakers Bureau; Janssen: Other: advisory board, Speakers Bureau. Hong:Dana Farber Cancer Institute: Employment; Merck: Consultancy. Scott:Roche/Genentech: Research Funding; Celgene: Consultancy; Janssen: Consultancy, Research Funding; NanoString: Patents & Royalties: Named inventor on a patent licensed to NanoSting [Institution], Research Funding. Amengual:Appia Pharmaceuticals: Research Funding; Epizyme: Speakers Bureau. Leonard:BeiGene: Consultancy; Miltenyi: Consultancy; Sandoz: Consultancy; Gilead: Consultancy; Celgene: Consultancy; ADC Therapeutics: Consultancy; MorphoSys: Consultancy; ADC Therapeutics: Consultancy; Epizyme, Inc: Consultancy; Miltenyi: Consultancy; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy; Karyopharm Therapeutics: Consultancy; Akcea Therapeutics: Consultancy; Merck: Consultancy; Nordic Nanovector: Consultancy; Akcea Therapeutics: Consultancy; Bayer Corporation: Consultancy; Sandoz: Consultancy; MorphoSys: Consultancy; Gilead: Consultancy; BeiGene: Consultancy; AstraZeneca: Consultancy; Nordic Nanovector: Consultancy; Sutro Biopharma: Consultancy; Merck: Consultancy. Friedberg:Bayer: Honoraria, Other: Data & Safety Monitoring Committee; Acerta: Other: Data & Safety Monitoring Committee. Kostakoglu:F. Hoffman-La Roche: Consultancy; Genentech: Consultancy. Jurczak:Morphosys: Research Funding; Bayer: Research Funding; Roche: Research Funding; Incyte: Research Funding; Gilead: Research Funding; Celgene Corporation: Research Funding; Sandoz: Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novo Nordisk: Research Funding; Servier: Research Funding; Takeda: Research Funding; TG Therapeutics: Research Funding; Celtrion: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Loxo: Membership on an entity's Board of Directors or advisory committees, Research Funding. Yamamoto:Bristol-Myers Squibb: Consultancy, Honoraria; Bayer: Research Funding; Celgene Corporation: Consultancy, Honoraria, Research Funding; Mundipharma: Consultancy, Honoraria, Research Funding; Astra-Zeneca: Consultancy, Research Funding; Eisai: Consultancy, Honoraria, Research Funding; Meiji Seika Pharma: Consultancy, Honoraria; ARIAD: Research Funding; MSD: Consultancy, Honoraria; Gilead Sciences: Research Funding; Ono: Consultancy, Honoraria, Research Funding; SymBio: Research Funding; HUYA/IQVIA Services Japan: Consultancy, Honoraria; AbbVie: Consultancy, Research Funding; Chugai: Consultancy, Honoraria, Research Funding; Pfizer: Honoraria; Sumitomo Dainippon: Honoraria; Incyte: Research Funding; Janssen: Honoraria; Kyowa Kirin: Honoraria; Novartis: Honoraria, Research Funding; Otsuka: Honoraria; Sanofi: Honoraria; Solasia Pharma: Research Funding; Takeda: Consultancy, Honoraria, Research Funding. Czuczman:Celgene Corporation: Employment, Equity Ownership. Russo:Celgene Corporation: Employment, Equity Ownership. Hudak:Celgene Corporation: Employment, Equity Ownership; Novartis: Employment, Equity Ownership. Zhang:Celgene Corporation: Employment, Equity Ownership. Wade:Celgene: Employment, Equity Ownership. Kahl:ADC Therapeutics: Consultancy, Research Funding; BeiGene: Consultancy; TG Therapeutics: Consultancy; Seattle Genetics: Consultancy. Vitolo:Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; F. Hoffmann-La Roche: Speakers Bureau; Juno Therapeutics: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Kite: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. OffLabel Disclosure: Yes, these trials discuss off-label clinical trial investigation of lenalidomide plus R-CHOP in patients with newly diagnosed diffuse large B-cell lymphoma.

Background: Activation induced cytidine deaminase (AICDA or AID) causes somatic hypermutation (SHM) of the immunoglobulin heavy chain variable genes (IGHV). It has been widely hypothesized that aberrant targeting of AICDA creates additional driver mutations and intra-clonal heterogeneity which enables clonal evolution and thus disease progression. This hypothesis predicts that greater AICDA-mediated intraclonal heterogeneity will be associated with shortened progression free survival (PFS). To definitively test this hypothesis that AICDA-mediated heterogeneity is linked to risk of progression, we evaluated available samples from the largest US-based phase 3 trial of untreated follicular lymphoma patients treated with CHOP-based therapies, SWOG trial S0016. Methods: We have previously shown that ultradeep sequencing of two genes, the expressed IGHV and the 5' UTR of the translocated BCL2 allele, provide unrelated measures of AICDA-mediated genetic heterogeneity (Spence, J Immunol. 2014). Furthermore, the number of AICDA-mediated mutations in the 5' UTR of BCL2, but not in IGHV, correlates with the number of AICDA-mediated mutations at other known AICDA sites throughout the genome (such as PIM1, BCL6, RHOA, etc). Genomic DNA was prepared from all available paraffin-embedded specimens. Ultra-deep, amplicon-based sequencing (~10,000x) with internal controls to establish specimen-specific signal-to-noise parameters allowed sensitive and specific detection of sequence variants at 0.2% (FDR 1%). Results: For subjects with (152) and without (419) available specimens, the median duration of follow-up (11.3 years), the number of patients who progressed (60%), and other patient characteristics (demographics, histology, stage, FLIPI) were indistinguishable. Sequencing data that fulfilled strict quality metrics for low frequency variants were obtained for >75% of the specimens (114 for BCL2; 120 for IGHV); further analysis was restricted to these subjects. The extent of intraclonal variation within both the IGHV and the 5' UTR of BCL2 was highly variable. For BCL2, a median of 7 mutations/case were detected (range 0-61); the mutations were highly skewed to the RCYW motif (p<0.001), the preferred target of AICDA. These mutations defined a median of 5 subclones/case (range 1-22). The clonal IGHV was somatically mutated (<0.98 germline identity) in 94% of samples (median 0.89). For IGHV, a median of 113 subclones/case were detected (range 0-1531). Consistent with our prior study, no correlation was seen between the number of mutations detected in the IGHV and BCL2 or the number of subclones defined by IGHV and BCL2. Neither the number of mutations in nor the number of subclones defined by BCL2 or IGHV were prognostic. Cox regression showed no relationship between PFS and mutation number or subclone count based on either IGHV or BCL2 (hazard ratios are indistinguishable from 1; parameters were treated both as a continuous variables and dichotomized as quartiles). Furthermore, receiver operator curves did not suggest a cut point for any of these measures that would predict disease progression at any time (areas under the curve are indistinguishable from 0.5). Conclusions: Several measures of AICDA-mediated mutation and resulting subclonal heterogeneity were not found to be prognostic in previously untreated, advanced stage FL treated with CHOP-based regimens. In contrast, AICDA-mediated mutations have been reported to accrue during transformation from low grade FL to large cell lymphoma. This paradox calls for a more refined model to explain the role of AICDA in the progression of FL. Support: NIH/NCI grants U10CA180888, U10CA180819, U10CA180821, R21CA198072(WRB); and in part by GlaxoSmithKline. Disclosures Rimsza: NanoSting: Patents & Royalties: Named inventor on a patent licensed to NanoSting [Institution]. Leonard:Bayer Corporation: Consultancy; AstraZeneca: Consultancy; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy; Sandoz: Consultancy; ADC Therapeutics: Consultancy; Miltenyi: Consultancy; BeiGene: Consultancy; Sutro Biopharma: Consultancy; Celgene: Consultancy; Nordic Nanovector: Consultancy; Gilead: Consultancy; Karyopharm Therapeutics: Consultancy; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy; Bayer Corporation: Consultancy; Celgene: Consultancy; Epizyme, Inc: Consultancy; Merck: Consultancy; MorphoSys: Consultancy; AstraZeneca: Consultancy; Epizyme, Inc: Consultancy; Akcea Therapeutics: Consultancy; Miltenyi: Consultancy; ADC Therapeutics: Consultancy; BeiGene: Consultancy; Karyopharm Therapeutics: Consultancy; Merck: Consultancy; Sandoz: Consultancy; Gilead: Consultancy; Akcea Therapeutics: Consultancy; MorphoSys: Consultancy; Nordic Nanovector: Consultancy; Sutro Biopharma: Consultancy. Fisher:Celgene: Consultancy; Barclays: Honoraria; AstraZeneca: Consultancy; prIME: Honoraria. Smith:Portola Pharmaceuticals: Research Funding. Friedberg:Bayer: Honoraria, Other: Data & Safety Monitoring Committee; Acerta: Other: Data & Safety Monitoring Committee.

INTRODUCTION Complete staging via bone marrow assessment is standard of practice for most newly diagnosed non-Hodgkin lymphoma (NHL) patients, though the methods and patterns of bone marrow assessment vary in clinical practice. The 2014 Lugano Classification recommends that in diffuse large B cell lymphoma (DLBCL), positron emission tomography-computed tomography (PET/CT) alone can designated advanced-stage disease in many, but not all cases. For most other NHL subtypes, obtaining bone marrow biopsy (BMB) remains recommended. We aimed to assess clinical practice patterns of marrow assessment and the performance of PET/CT in the clinical setting. METHODS The Lymphoma Epidemiology of Outcomes (LEO) cohort is a prospective cohort from 8 academic medical centers. All patients were enrolled in the cohort within 6 months of diagnosis, and prospectively followed. Patients with lymphoma enrolled in the cohort between July 2015 and June 2017 were included for study. Baseline clinical characteristics at diagnosis, whether BMB and/or PET/CT were performed, and the result of these assessments were extracted from the database. Bone marrow involvement on PET/CT was abstracted via review of radiology reports. No central review of images was utilized. RESULTS In total, 3,251 patients were included, consisting of the following subtypes: DLBCL (n=1,098), follicular lymphoma (FL n=730), mantle cell lymphoma (MCL n=302), T-cell lymphoma (TCL n=278), marginal zone lymphoma (MZL n=269), other NHL (n=505) and composite lymphoma (n=69). Other clinical characteristics are shown in table 1. Staging BMB was obtained in 78% of patients, PET/CT was obtained in 56%, both BMB and PET/CT were obtained in 46% while neither were obtained in 9% (table 1). There were significant differences in lymphoma subtype between patients having any bone marrow assessment vs no bone marrow assessment (p<0.0001). MCL (96%) and DLBCL (94%) most frequently had any bone marrow assessment, while MZL was least frequently assessed (84%). Patients undergoing any bone marrow assessment had higher median lactate dehydrogenase (247 U/L vs 206 U/L, p=0.0002). Among the 8 enrolling medical centers, the frequency of bone marrow biopsy at diagnosis ranged from 53% to 86%, and the frequency of PET/CT at diagnosis ranged from 34% to 94% (p<0.0001, table 1). Among patients with DLBCL who had positive bone marrow by either PET/CT or BMB (N=107), 41% (44/107) were positive by BMB only, 19% (20/107) were positive by PET/CT only, and 40% (43/107) were positive by both. Figure 1 shows results of similar analyses for FL, MCL, MZL, and TCL. Using BMB as a gold standard for marrow involvement, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of PET/CT for marrow assessment in DLBCL is 49%, 90%, 68% and 91%, respectively. Data for other subtypes are shown in table 2. Patients undergoing both PET/CT and BMB had lower median LDH (231 U/L vs 254 U/L, p=0.0032) than those undergoing one or neither assessments. CONCLUSION Overall, 91% of all patients with newly diagnosed NHL had bone marrow assessments via either PET/CT, BMB or both. The significant variation in the frequency of BMB and PET/CT use among the 8 centers reflects a lack of clear consensus on staging practices regarding bone marrow assessment. The sensitivity of PET/CT for detection of marrow involvement was less than 50% across all subtypes. It is possible the sensitivity of PET/CT could be improved via a centralized review process of the images, as is performed in some clinical trials, however practical approaches for implementing such reviews in clinical practice have not been developed. Between 92-100% of all positive bone marrows were detected by BMB, except in cases with DLBCL in which 19% of positive bone marrows were missed by BMB but detected by PET/CT. Thus, in our analysis, BMB more reliably captured marrow involvement that PET/CT in all subtypes in which both assessments were performed. However, neither PET/CT nor BMB alone were able to identify all cases of bone marrow involvement and use of both modalities may be necessary in cases where marrow involvement would have clinically important implications. Disclosures Rutherford: Juno Therapeutics Inc: Consultancy, Honoraria; Janssen Scientific Affairs: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria; Verastem: Consultancy, Honoraria; Karyopharm: Honoraria, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Heron: Consultancy, Honoraria. Kahl:ADC Therapeutics: Consultancy, Research Funding; Seattle Genetics: Consultancy; TG Therapeutics: Consultancy; BeiGene: Consultancy. Lossos:Janssen Scientific: Membership on an entity's Board of Directors or advisory committees; NIH: Research Funding; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees. Friedberg:Acerta: Other: Data & Safety Monitoring Committee; Bayer: Honoraria, Other: Data & Safety Monitoring Committee. Casulo:Celgene: Research Funding; Roche: Other: Travel, accommodation, expenses; Gilead: Honoraria, Other: Travel, accommodation, expenses. Cohen:Astra Zeneca: Research Funding; Takeda Pharmaceuticals North America, Inc.: Research Funding; Hutchison: Research Funding; Gilead/Kite: Consultancy; Bristol-Meyers Squibb Company: Research Funding; LAM Therapeutics: Research Funding; UNUM: Research Funding; Lymphoma Research Foundation: Research Funding; ASH: Research Funding; Seattle Genetics, Inc.: Consultancy, Research Funding; Janssen Pharmaceuticals: Consultancy; Genentech, Inc.: Consultancy, Research Funding. Nastoupil:TG Therapeutics: Honoraria, Research Funding; Novartis: Honoraria; Spectrum: Honoraria; Celgene: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Genentech, Inc.: Honoraria, Research Funding; Gilead: Honoraria; Bayer: Honoraria. Flowers:Denovo Biopharma: Consultancy; Spectrum: Consultancy; National Cancer Institute: Research Funding; Optimum Rx: Consultancy; Burroughs Wellcome Fund: Research Funding; Acerta: Research Funding; Bayer: Consultancy; BeiGene: Consultancy, Research Funding; Eastern Cooperative Oncology Group: Research Funding; TG Therapeutics: Research Funding; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy, Research Funding; Gilead: Consultancy, Research Funding; Karyopharm: Consultancy; AstraZeneca: Consultancy; Pharmacyclics/Janssen: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; V Foundation: Research Funding; Millenium/Takeda: Research Funding; Celgene: Consultancy, Research Funding. Cerhan:Janssen: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; NanoString: Research Funding. Martin:Sandoz: Consultancy; Karyopharm: Consultancy; Celgene: Consultancy; Teneobio: Consultancy; I-MAB: Consultancy; Janssen: Consultancy.

Key Points Five-year follow-up of S1106 demonstrates similar efficacy, MRD negativity, and 5-year survival with RH or RB, but RH was more toxic than RB. RB showed excellent efficacy and survival and less toxicity compared with a cytarabine-based regimen in transplant-eligible MCL patients.

Abstract Background Disease characteristics, treatment patterns, and outcomes of follicular lymphoma (FL) patients (pts) aged >80 years (yrs) are infrequently reported. Further, the original Follicular Lymphoma International Prognostic Index (FLIPI) has not been formally studied in pts aged >80 yrs. Also, whether FLIPI is associated with overall survival (OS) in pts aged >80 yrs is unknown. Patients/Methods We used the National LymphoCare Study—a Genentech-sponsored, prospective, multicenter registry of FL pts across the United States without study-specific treatment—to comprehensively analyze FL pts aged >80 yrs. Using Pearson chi-squared tests, associations of age groups with disease characteristics and overall response rate (ORR) were examined. Median progression-free survival (PFS) and OS by treatment regimen were estimated using the Kaplan-Meier method. Cox proportional hazards regression that were adjusted for baseline disease factors were used to assess treatment differences in PFS, lymphoma-related mortality (LRM, which includes both disease and treatment-related deaths), and OS, as well as the significance of age by treatment interactions. FLIPI and a prognostic model that was constructed based on the findings were used to predict outcomes. Results Of 2649 evaluable pts, 209 (8%) were aged >80 yrs. Compared with pts aged ≤60, pts aged >80 yrs were more likely to be Caucasian, to have worse performance status, to have lower hemoglobin (Hgb) value (<12 g/dL), to have less advanced stage, and were less likely to be treated at academic institutions. When treated, pts aged >80 yrs had lower ORR compared with younger pts and were less likely to receive rituximab + chemotherapy (P <.001) or anthracyclines (P <.001). Use of maintenance rituximab was not significantly different between pt groups when rituximab induction was given (61% for pts aged ≤60, 38% for pts aged >80, P=.11), but it was more frequent in pts aged >80 yrs when rituximab + chemotherapy induction was administered (44% for pts aged ≤60, 59% for pts aged >80, P=.04). After adjusting for maintenance use, sex, and baseline factors, age significantly differentiated PFS impact of observation, rituximab monotherapy, and rituximab + chemotherapy (P=.01). No treatment regimen provided superior PFS or OS in pts aged >80 yrs. With a median follow-up of 6.5 yrs for all pts (4.3 yrs for pts aged >80 yrs), 5-year OS was 59% and 92%for patients aged >80 and ≤60 yrs, respectively. OS in pts aged >80 yrs varied based on FLIPI score (log-rank test, P=.01; Figure 1). Interestingly, the percentage of deaths that were disease-related was 40% in pts aged >80 yrs, which was comparable to the percentage in pts aged ≤60 yrs of 48%. Cox modeling showed that lower Hgb, B symptoms, and male sex predicted worse OS (P<.01) but not PFS in pts aged >80 yrs. Recognizing that males have inferior OS compared with females in the general population, we constructed a prognostic model composed only of B symptoms and Hgb level <12 (low risk=no factors; high risk=1 or more factors; P<.0001; Figure 2). FLIPI and the proposed prognostic model significantly differentiated both OS and LRM (Table 1). Conclusions In the largest, prospectively published study of FL pts aged >80 yrs, OS, PFS, ORR, and treatment selection varied compared with younger pts. Surprisingly, the proportion of deaths attributed to lymphoma in these older FL pts was 40%. FLIPI was associated with outcome in pts aged >80 yrs and so was a proposed prognostic model comprising lower Hgb and B symptoms. Independent validation of this model is required, and additional prospective studies that are designed for the oldest old are warranted. Disclosures: Nabhan: Genentech Inc.: Advisory Board Other, Honoraria. Byrtek:Genentech, a member of the Roche group: Employment, Equity Ownership; Roche: Equity Ownership, stock options, stock options Other. Dawson:Genentech: Employment; Roche: Equity Ownership. Link:Genentech: Consultancy; Millenium: Consultancy; Pharmacyclics: Consultancy; Spectrum: Consultancy; Genentech: Research Funding; Millenium: Research Funding; Pharacyclics: Research Funding. Zelenetz:GSK: Consultancy; Celgene: Consultancy; Cephalon: Consultancy; Gilead: Consultancy; Seattle Genetics: Consultancy; Sanofi-Aventis: Consultancy; Genentech: Research Funding; GSK: Research Funding; Roche: Research Funding; Cancer Genetics: Scientific Advisor Other. Cerhan:Genentech: Scientific Advisory Board of the National LymphoCare Study Other. Flowers:Abbott, Celgene, Millennium/Takeda, Sanofi, Spectrum, Janssen: Research Funding; Celgene, Genentech Bio-oncology: Consultancy.

Abstract Background: TP53 is reported to be mutated in about 20% of transformed and/or relapsed follicular lymphoma (FL) specimens but in fewer than 5% of pre-treatment FL specimens. The disparity in the reported prevalence of TP53 mutations at diagnosis versus transformation/relapse suggests that TP53-mutated subpopulations, which are too small for detection, might be present at the time of diagnosis in tumors destined to relapse. To test this hypothesis, we developed a more sensitive assay for TP53 mutations and applied the assay to SWOG S0016, a phase III randomized intergroup trial of CHOP chemotherapy plus rituximab (R-CHOP) compared with CHOP chemotherapy plus 131-iodine tositumomab (radio-immunotherapy (RIT)-CHOP) for previously untreated follicular non-Hodgkin lymphoma. Methods: Formalin Fixed Paraffin Embedded (FFPE) biopsies were available for 213/571 enrollees. 147 samples fulfilled inclusion criteria: 1) sufficient DNA for 3 PCR-reactions each at 250 ng gDNA (~40,000 diploid equivalents; 5'UTR and all exons of TP53 were amplified in 3 multiplexed reactions to obtain consistently sized amplicons); 2) appropriate size distribution of DNA products after library preparation (~300 bp). To maintain specificity with high read-coverage, each PCR included an amplicon of eUCR41 (eukaryotic ultra-conserved region) to provide specimen-specific metrics of DNA-damage and sequencing noise. Sequence reads (Ilumina 300 nt paired end) were merged, mapped to reference (>10,000x coverage), and single nucleotide variants (SNV) were called using LoFreq based on case and base-change error thresholds (from the eUCR41 data). Pathogenicity of each TP53 sequence variant was based on a consensus of the Seshat and IARC databases. Variant Allele Frequencies (VAF) of passenger SNVs (5'UTR of BCl2) allowed normalization to the minimum tumor fraction. Results: A total of 73 SNVs within TP53 were detected in 147 FFPE specimens (80 RIT-CHOP; 67 R-CHOP); the SNVs in 34 patients (23%; 17-30% 95% CI) created missense or nonsense mutations which met criteria for pathogenicity. The VAF for these SNVs ranged from 0.008 to 0.7 (median 0.02) and 82% had a VAF of less than 0.1. Among the 34 patients with a pathogenic TP53 mutation, no relationship was observed between the VAF and time to progression. The group of 34 patients with a pathogenic TP53 mutation had a shortened Progression Free Survival (PFS) (HR=1.68; p=0.035) and Overall Survival (OS) (HR=2.02; p=0.045). However, the relationship between TP53 mutations and PFS depended on treatment: for the R-CHOP arm, the pathogenic TP53 mutations were not associated with PFS (10-year PFS 44% vs 42%); in contrast, for the RIT-CHOP arm, pathogenic TP53 mutations were associated with a shortened PFS (10 year PFS 27% vs 65%; HR=3.2; p=0.001) (see figure). Furthermore, among patients with no detectable pathogenic TP53 mutation, RIT-CHOP was associated with a longer PFS than R-CHOP (10 year PFS 65% vs 44%; HR=0.58; p=0.046). Conclusions: Using specimens from SWOG S0016, we find that pathogenic TP53 mutations are present in 23% of untreated, advanced stage FL specimens, a considerably higher fraction than reports based on less sensitive methods. Long term follow-up of S0016 has shown that the RIT-CHOP arm had a small but statistically significant improvement in the 10-year PFS compared to R-CHOP (Shadman 2018). We now show that the interaction of RIT and TP53-status substantially affects PFS. First, in the cohort without a detectable TP53 mutation, a longer PFS was observed with RIT-CHOP than R-CHOP. Second, in the cohort with a detectable TP53 mutation, a shorter PFS was observed with RIT-CHOP than R-CHOP. This observation is consistent with the well-defined role of TP53 as the mediator of the apoptotic response to ionizing radiation. Therefore, an assay which detects subclonal populations with TP53 mutations defines two cohorts for which the inclusion of radio-immunotherapy had substantial and opposite effects on the risk of progression. Finally, this identification of subclonal TP53 mutations as a predictive biomarker highlights that preserving specimens from clinical trials to mine with new technologies can be key to the advancement of precision medicine. We wish to recognize the late Dr. Oliver Press for his central role in S0016 and his many contributions to SWOG. Support: NIH/NCI grants U10CA180888, U10CA180819, U10CA180821, R21CA198072 (RB); and in part by GlaxoSmithKline. Figure. Figure. Disclosures Rimsza: NanoString: Other: Inventor on the patent for the Lymph2Cx assay. Leonard:Juno: Consultancy; ADC Therapeutics: Consultancy; Pfizer: Consultancy; Gilead: Consultancy; Sutro: Consultancy; Biotest: Consultancy; United Therapeutics: Consultancy; BMS: Consultancy; Bayer: Consultancy; Genentech/Roche: Consultancy; Celgene: Consultancy; MEI Pharma: Consultancy; AstraZeneca: Consultancy; Karyopharm: Consultancy; Novartis: Consultancy. Smith:BMS: Consultancy; Portola: Honoraria. Friedberg:Bayer: Honoraria.