Peterson, Jennifer

Abstract Background Yttrium-90 ibritumomab tiuxetan [(90)Y-IT; Zevalin] is a radio-immunoconjugate (RIC) which targets CD20. This study evaluates the utilization and cost-effectiveness of (90)Y-IT in the first line treatment for patients with previously untreated low-grade FL (UFL) and marginal zone lymphoma (UMZL) treated at our institution with (90)Y-IT. Methods We utilized the Advanced Text Explorer (ATE) and the Lymphoma SPORE databases to identify two groups of patients with UFL, WHO grade 1-2, and UMZL who received treatment with either (90)Y-IT or bendamustine plus rituximab (BR) at Mayo Clinic Cancer Center between January 2003 and December 2019. We excluded all patients who had >25% bone marrow involvement with lymphoma for the BR group as this was a requirement for (90)Y-IT treatment. Inverse propensity weighting was utilized to balance the groups for baseline patients and disease characteristics. We use progression-free survival (PFS) as a denominator for the cost effectiveness/utilization evaluation. We identified meaningful and retrospectively measurable outcomes to compare between the groups. we extracted the following data; number of clinic visits in the first year after therapy, emergency room visits, number of hospital admissions, number of hospitalization days, numbers of days on the floor and ICU, number of infections, number of neutropenic fever hospitalizations, number of C-difficile events, number of blood products transfusions, overall use of growth factors due to therapy induced neutropenia, average number of times a growth factor was used, and the number of therapeutic use days. We defined days of therapeutic use as the number of days a treatment was administered on. We also calculated the average cost of the induction treatment when utilizing either (90)Y-IT or BR. The therapeutic cost included only the cost of the medications/therapies and their administration. Results Our cohort consists of a total of 143 patients - 64% (92/143) received BR and 36% (51/143) received (90)Y-IT (see Table-1 for clinical characteristics).The median follow-up from the time of therapeutic administration for the (90)Y-IT group was 5.3 years (95% CI; 4.2, 6.2) with one death and 4.7 years (95% CI; 3.9, 4.9) for the BR group with 6 deaths. The ORR was 100% in (90)Y-IT group with 94% achieving complete response (CR) while ORR in the BR group was 98% with 95% achieving CR. Rituximab maintenance was utilized in 33% of BR patients compared to only 6% in patients who received (90)Y-IT, p=0.002. After utilizing inverse propensity weighting (Figure-1), 5 years PFS was 76% for the (90)Y-IT group and 75% for the BR group, p=0.63 (Figure-2). We evaluated the average treatment effect of (90)Y-IT compared to BR on utilization outcomes, Table-2. (90)Y-IT required an average of 4.5 clinic visits less within the first year after treatment compared to BR group, p<0.001. (90)Y-IT patients had an average of 10 days less of therapeutic use days compared to the BR group, p<0.001. Patienta had similar admission rates to the hospital in both groups. However, when patients were admitted to the hospital in the first year after treatment, those who received (90)Y-IT spent an average of 1.5 days less in the hospital compared to the BR group, p=0.046. The overall use of growth factors was 40% less in the (90)Y-IT group as compared to the BR group, p<0.001. The therapeutic cost of induction of (90)Y-IT was 54% less than that of 6 cycles of BR. Transformation to a high grade of lymphoma was seen in 4 patients in the BR group and 2 patients in the (90)Y-IT group. There was only one case of myelodysplastic syndrome in the BR group and none in the (90)Y-IT group. Conclusion Radio-immunoconjugate therapy with (90)Y-IT is a very convenient and cost-effective treatment for low-grade UFL and UMZL. This is especially important amidst the COVID-19 pandemic as it requires less contact with the health system with decreased number of therapeutic days, clinic visits, use of growth factors and number of hospitalization days. The cost of the therapeutic agents and their administration was also significantly lower for the (90)Y-IT which could help reducing the burden on the health system. Figure 1 Figure 1. Disclosures Cerhan: Regeneron Genetics Center: Other: Research Collaboration; Genentech: Research Funding; Celgene/BMS: Other: Connect Lymphoma Scientific Steering Committee, Research Funding; NanoString: Research Funding. Tun: Mundipharma, Celgene, BMS, Acrotech, TG therapeutics, Curis, DTRM: Research Funding; Gossamer Bio, Acrotech: Consultancy. OffLabel Disclosure: We are describing the use of Yttrium-90 ibritumomab tiuxetan in the first line setting in comparison to the bendamustine plus rituximab which is the standard of care

Abstract Purpose: Axicabtagene ciloleucel (axi-cel) is an anti-CD19 chimeric antigen receptor T-cell (CAR-T) therapy utilized for patients with non-Hodgkin lymphoma (NHL) refractory to at least 2 lines of therapy. F-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) is used to evaluate disease extent prior to CAR-T infusion at two time points: pre-leukapheresis (pre-leuk) approximately 6 weeks prior to CAR-T infusion, and pre-lymphodepletion chemotherapy (pre-LD) approximately 1 week prior to CAR-T infusion. We hypothesized that PET/CT characteristics beyond Lugano criteria, such as metabolic tumor volume (MTV), total lesion glycolysis (TLG), SUV maximum (SUVMax), and changes in these parameters from pre-leuk to pre-LD, may predict for progressive disease (PD), death, and treatment toxicity after CAR-T infusion. Methods: Patients with NHL who received axi-cel on a prospective registry at Mayo Clinic Rochester were included. Lesions on pre-leuk and pre-LD PET/CT scans were segmented with a fixed absolute SUVMax threshold of 2.5 using a semi-automated workflow (LesionID, MIM Software Inc.) with manual modification to exclude physiologic uptake as needed. MTV, TLG, SUVMax, number of lesions, and other lesion characteristics were assessed for each PET/CT, and changes from pre-leuk to pre-LD were calculated. Lesions were categorized as either nodal, spleen, bone, parenchymal (i.e. liver, lung), or soft tissue (i.e. subcutaneous, muscle), and MTV was calculated for each category. Univariate Cox modeling was used to associate relative and directional change in metabolic and volumetric PET/CT characteristics with PD and death, after adjusting for bridging therapy. LASSO method was used for multivariable model selection. Pre-LD PET/CT characteristics were also assessed for association with presence and duration of cytokine release syndrome (CRS), grade 3+ immune effector cell-associated neurotoxicity syndrome (ICANS), tocilizumab (toci) use, and corticosteroid use. Results: From 2018-2020, axi-cel was delivered to 69 patients. Histology included diffuse large B-cell lymphoma (57%), transformed follicular lymphoma (23%), or high-grade lymphoma (19%). Pre-leuk and pre-LD PET/CT scans were performed a median of 46 days and 7 days prior to CAR-T infusion, respectively. Forty patients (58%) received bridging therapy between scans, including 9 (13%) receiving radiotherapy. At a median follow-up of 13 months, 39 (57%) had died and 46 (67%) had PD. Sixty patients (87%) developed CRS following CAR-T infusion for a median duration of 5 days. Presence of pre-LD parenchymal disease was associated with longer duration CRS (p=0.032). Thirty-seven patients (54%) developed ICANS for a median duration of 4.5 days, including 12 (32%) with grade 3+ ICANS. Greater pre-LD total MTV was associated with higher risk of grade 3+ ICANS (p=0.042). Greater pre-LD SUVMax was associated with longer duration ICANS (p=0.032). Nineteen (28%) patients required toci. Greater pre-LD total MTV, SUVMax, TLG, and volume of the largest lesion were associated with increased use of toci (p<0.05 for all). Greater pre-LD total MTV and TLG of the largest lesion were associated with increased use of corticosteroid (p<0.05 for each). While no individual pre-leuk or pre-LD PET/CT characteristics were associated with risk of PD or death, increases from pre-leuk to pre-LD in total MTV, total TLG, parenchymal MTV, and nodal MTV were associated with increased risk of PD (Figure 1). Similarly, increases from pre-leuk to pre-LD in parenchymal MTV, nodal MTV, TLG of the largest lesion, and total number of lesions were associated with increased risk of death (p<0.05 for all). LASSO analysis identified increasing extranodal MTV (≥25% increase) and increasing TLG of the largest lesion (≥10% increase) as strong predictors of death (AUC 0.74, Table 1). Kaplan-Meier plots were generated for overall and progression-free survival using these risk factors (Figure 2). Additional patients and follow-up will be presented. Conclusions: Patients with greater pre-LD MTV had higher risk of grade 3+ ICANS and use of toci or corticosteroids. Increasing metabolic disease burden during CAR-T manufacturing is associated with increased risk of PD and death. A two variable risk score using increasing extranodal disease and increasing TLG of the largest lesion may stratify prognosis prior to CAR-T and inform treatment paradigms. Figure 1 Figure 1. Disclosures Bennani: Verastem: Other: Advisory Board; Purdue Pharma: Other: Advisory Board; Daichii Sankyo Inc: Other: Advisory Board; Kyowa Kirin: Other: Advisory Board; Vividion: Other: Advisory Board; Kymera: Other: Advisory Board. Paludo: Karyopharm: Research Funding. Wang: Genentech: Research Funding; LOXO Oncology: Membership on an entity's Board of Directors or advisory committees, Research Funding; Eli Lilly: Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; InnoCare: Research Funding; Novartis: Research Funding; MorphoSys: Research Funding; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees. Ansell: Bristol Myers Squibb, ADC Therapeutics, Seattle Genetics, Regeneron, Affimed, AI Therapeutics, Pfizer, Trillium and Takeda: Research Funding. Lin: Gamida Cell: Consultancy; Janssen: Consultancy, Research Funding; Legend: Consultancy; Novartis: Consultancy; Celgene: Consultancy, Research Funding; Sorrento: Consultancy; Bluebird Bio: Consultancy, Research Funding; Takeda: Research Funding; Kite, a Gilead Company: Consultancy, Research Funding; Merck: Research Funding; Vineti: Consultancy; Juno: Consultancy.

7561 Background: Phospholipid ethers (PLE) provide a novel mechanism to specifically target tumor cells leveraging high lipid raft content in their cell membranes. PLE/phospholipid drug conjugates are specifically designed to have high affinity to lipid rafts which upon binding results in trans-membrane flipping with the ability to deliver an attached warhead directly to the cytosol. CLR 131 (I-131-CLR1404) is a novel PLE molecule armed with I-131 resulting in targeted tumor cell radiotherapy which is being examined in relapsed or refractory WM through an open-label, Phase 2 trial, CLOVER-1 (NCT02952508). Methods: The primary objective of this study is to determine the efficacy and safety of CLR 131 in select B-cell malignancies. Eligibility criteria for WM pts include receipt of at least 2 prior treatment regimens unless ineligible to receive standard agents and have measurable disease: either IgM or extramedullary disease. CLR 131 is administered in up to 4 IV infusions (15-20 min) over 3 months. Adverse events (AEs) are graded by NCI-CTCAE v4.03; responses are assessed by the VIth WM Criteria for Response Assessment [Owen 2013]. Results: 6 pts with WM were enrolled in the study with data current as of 8 Jan 2021. The median age was 69 (range 54-81) with 4 females and 2 males who had a median of 2 prior regimens (range 1-5) and received a mean total body dose of 92.76 mCi CLR 131. 3 of 6 patients were MYD88 wild type (WT) of which 2 were dual WT (MYD88 WT & CXCR4 WT). The overall response rate (ORR) was 100% and the major response rate (MRR) was 83%, including 1 pt with a CR, 4 PR, and 1 MR. For those pts who were dual WT, the MRR was 100% and 1 pt who was MYD88 WT (CXCR4 is unknown) had a complete response. The median time to initial response was 48 days. Median duration of response (DOR) and treatment free remission (TFR) have not been reached; ongoing mean DOR is 335 days and mean TFR is 384 days. 100% of MYD88 WT patients have exceeded 6.5 months of follow up with average TFR of 18.1 months. The primary treatment emergent AEs in pts with WM included fatigue and cytopenias, in line with prior experience with CLR 131 in other B-cell malignancies. The most commonly observed cytopenias included Grade 3 or 4 thrombocytopenia (100%), neutropenia (83%), anaemia (66%) and decreased white blood cell count (33%). Of note, no cases of bleeding or febrile neutropenia were observed. Conclusions: Initial results for CLR 131 show efficacy across multiple WM patient genotypes including dual WT patients with durable DOR and TFR after 2 to 4 infusions. CLR 131 represents a novel and promising approach to the treatment of MYD88 WT patients who have a historical median time to progression of 1.3 years. These encouraging data led to the pivotal global CLOVER-WaM trial (N=50) in WM patients who have failed or had a suboptimal response to a Bruton Tyrosine Kinase inhibitor. CLOVER-WaM is currently enrolling. Clinical trial information: NCT02952508.

Stereotactic radiosurgery (SRS) involves the delivery of a highly conformal ablative dose of radiation to both benign and malignant targets. This has traditionally been accomplished in a single fraction; however, fractionated approaches involving five or fewer treatments have been delivered for larger lesions, as well as lesions in close proximity to radiosensitive structures. The clinical utilization of SRS has overwhelmingly involved photon-based sources via dedicated radiosurgery platforms (e.g., Gamma Knife® and Cyberknife®) or specialized linear accelerators. While photon-based methods have been shown to be highly effective, advancements are sought for improved dose precision, treatment duration, and radiobiologic effect, among others, particularly in the setting of repeat irradiation. Particle-based techniques (e.g., protons and carbon ions) may improve many of these shortcomings. Specifically, the presence of a Bragg Peak with particle therapy at target depth allows for marked minimization of distal dose delivery, thus mitigating the risk of toxicity to organs at risk. Carbon ions also exhibit a higher linear energy transfer than photons and protons, allowing for greater relative biological effectiveness. While the data are limited, utilization of proton radiosurgery in the setting of brain metastases has been shown to demonstrate 1-year local control rates >90%, which are comparable to that of photon-based radiosurgery. Prospective studies are needed to further validate the safety and efficacy of this treatment modality. We aim to provide a comprehensive overview of clinical evidence in the use of particle therapy-based radiosurgery.

OBJECTIVE Radiation-induced meningiomas (RIMs) are associated with aggressive clinical behavior. Stereotactic radiosurgery (SRS) is sometimes considered for selected RIMs. The authors investigated the effectiveness and safety of SRS for the management of RIMs. METHODS From 12 institutions participating in the International Radiosurgery Research Foundation, the authors pooled patients who had prior cranial irradiation and were subsequently clinically diagnosed with WHO grade I meningiomas that were managed with SRS. RESULTS Fifty-two patients underwent 60 SRS procedures for histologically confirmed or radiologically suspected WHO grade I RIMs. The median ages at initial cranial radiation therapy and SRS for RIM were 5.5 years and 39 years, respectively. The most common reasons for cranial radiation therapy were leukemia (21%) and medulloblastoma (17%). There were 39 multiple RIMs (35%), the mean target volume was 8.61 ± 7.80 cm 3 , and the median prescription dose was 14 Gy. The median imaging follow-up duration was 48 months (range 4–195 months). RIM progressed in 9 patients (17%) at a median duration of 30 months (range 3–45 months) after SRS. Progression-free survival at 5 years post-SRS was 83%. Treatment volume ≥ 5 cm 3 predicted progression (HR 8.226, 95% CI 1.028–65.857, p = 0.047). Seven patients (14%) developed new neurological symptoms or experienced SRS-related complications or T2 signal change from 1 to 72 months after SRS. CONCLUSIONS SRS is associated with durable local control of RIMs in the majority of patients and has an acceptable safety profile. SRS can be considered for patients and tumors that are deemed suboptimal, poor surgical candidates, and those whose tumor again progresses after removal.

AbstractIntroduction Vestibular schwannomas (VS) are slow growing tumors. Although there are a wide variety of available treatment options, these tumors are often initially observed. We aimed to establish the presenting symptoms and outcomes of patients treated with initial observation at our institution.Methods The medical records of patients with radiographically diagnosed VS were reviewed from 1989 to 2018. Actuarial estimates of radiographic tumor control and freedom of local therapy were calculated and compared using Cox regression analyses.Results A total of 360 patients were diagnosed with VS at our institution from 1989 through 2018 with a median age of 59.9 years. After radiographic diagnosis, 243 patients (67.5%) opted for initial observation. Local control at 1, 5, and 10 years was 91, 67, and 58%, respectively. On multivariable analysis, factors associated with shorter time to radiographic tumor progression included younger patient age (p = 0.016) and tumors with an extracanalicular component (p = 0.032). Regarding time until definitive treatment only larger baseline American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) tumor size predicted for earlier initiation of therapy (p < 0.001), although this was restricted to tumors with an extracanalicular component (p = 0.004), as opposed to purely internal auditory canal tumors (p = 0.839).Conclusion Many patients who were initially observed continued to have satisfactory local control rates at 10 years. In patients with extracanalicular tumors, larger AAO-HNS tumor measurements were associated with earlier radiographic tumor progression and shorter time to local therapy, with 7 mm serving as a potential threshold value for extracanalicular tumors. Younger patients and tumors with primarily an extracanalicular portion may warrant closer observation.

Background MZL is a low-grade non-Hodgkin's lymphoma (NHL) which involves lymph nodes, extranodal sites, or spleen. It is sensitive to radiation therapy, which is used in localized disease with curative intent. Yttrium-90 ibritumomab tiuxetan [(90)Y-IT; Zevalin] is a radio-immunoconjugate (RIC) that targets CD20. It is approved for relapsed/refractory low grade and follicular NHL. The data on its use in MZL is limited. We present long-term outcome of the largest reported cohort of MZL patients who received (90)Y-IT. Methods Medical records of patients who received treatment with (90)Y-IT at Mayo Clinic Cancer Center between January 2004 and December 2018 were analyzed. We selected patients with MZL and reviewed clinical data including age, gender, MZL type, clinical stage (Ann Arbor Staging System), treatment response, (90)Y-IT related adverse effects (AEs), as well as lymphoma and treatment related events. All patients received (90)Y-IT according to the standard treatment guidelines. Overall response rate (ORR) and complete response rate (CR) were calculated. Progression-free survival (PFS), time to next therapy (TTNT), and overall survival (OS) were analyzed using the Kaplan-Meier method. Results Twenty-one patients were identified (Table 1). The median age at diagnosis was 60 years (range, 11-81) and 71% (15/21) were female. 52% (11/21) were previously-untreated (UMZL) while 48% (10/21) were relapsed (RMZL). The median number of pretreatments in RMZL patients was 2 (range, 1-3). ECOG performance status at the time of treatment was 0 in 90% (19/21) and 1 in 10% (2/21). 62% (13/21) were stage III/IV disease at the time of (90)Y-IT therapy. The median follow-up was 8.5 years (95% CI; 4.5, 12.4); 17 (81%) patients remain alive. The ORR was 91% (19/21) with the two non-responders being in the RMZL group. The CR rate was 81% (17/21) and 65% (11/17) remain in CR at a median follow-up of 5.7 years (95% CI; 1.4, 11). Nine (43%) patients had a relapse during the study period. More relapses occurred in the RMZL group (7/10; 70%) compared to (2/11; 18%) in the UMZL group. Median PFS (whole cohort) was 10 years (95% CI; 2.1, NR) and TTNT (whole cohort) was not reached (NR) (95% CI; 2.1 years, NR). Median PFS was significantly higher in UMZL group compared to RMZL group NR (95% CI; 2.5 years, NR) vs 2.1 years (95% CI; 0.17, 9.9), respectively (Figure 1-A).Median OS (whole cohort) was 19.3 years (95% CI; 8.9, 19.3) without statistical difference in between UMZL group and RMZL group NR (95% CI; NR, NR) vs 16.6 years (95% CI; 9, 19.4), respectively (Figure 1-B). None of the 11 UMZL patients died at median follow up of 4.7 years (95% CI; 1.6, 9.2). All 4 deaths were in the RMZL group with 3 dying of transformation to high-grade lymphoma at 8, 22, and 25 months post-(90)Y-IT treatment. One patient died of myelodysplastic syndrome 7.3 years post-(90)Y-IT treatment while in CR. Toxicities were primarily hematologic. Grade ³3 neutropenia was observed in 6/21 (29%) patients with median time to nadir of 48.5 days (range, 19-70) and median time to recovery to normal absolute neutrophil count of 39.5 days (range, 7-476). Grade ³3 thrombocytopenia was observed in 3 (14%) patients with median time to nadir of 35 days (range, 19-357) and median time to recovery of 21 days (range, 2-538). Grade ³3 anemia was observed in only one patient. Only two patients required transfusions and growth factor support. Non-hematologic AEs included mild to severe fatigue in 4 patients. Conclusion RIC with (90)Y-IT is efficacious and well-tolerated in patients with previously untreated as well as relapsed MZL. As expected it appears to be more efficacious in previously untreated patients. Long-term complete remission (&gt;5 years) was observed in 52% of the study population (43% of UMZL and 9% of RMZL). Combination of efficacy, tolerability, and treatment schedule most convenient for patients makes (90)Y-IT a reasonable alternative to systemic therapy with immunotherapy, chemotherapy, or chemo-immunotherapy in management of MZL. Figure 1: (A) Progression-free survival; comparing time to progression or death after (90)Y-IT treatment between previously untreated patients (UMZL) and patients with relapsed MZL (RMZL), (B) Overall survival; comparing time to death from all causes after (90)Y-IT treatment between UMZL patients and RMZL patients. Disclosures Tun: Curis: Research Funding; TG Therapeutics: Research Funding; BMS: Research Funding; DTRM Biopharma: Research Funding; Celgene: Research Funding; Mundi-pharma: Research Funding. OffLabel Disclosure: The use of Yttrium-90 ibritumomab tiuxetan as a first line treatment for marginal zone lymphoma

Background Follicular lymphoma (FL) is the second most common lymphoma accounting for approximately 15% of all non-Hodgkin's lymphoma (NHL). Yttrium-90 ibritumomab tiuxetan [(90)Y-IT; Zevalin] is a radio-immunoconjugate (RIC) which targets CD20. It is approved in relapsed/refractory low-grade NHL and as consolidation after upfront induction chemoimmunotherapy for FL. This study analyzed patients with previously untreated (UFL) or relapsed/refractory low-grade FL (RFL) treated at our institution with (90)Y-IT. It represents the largest reported cohort for therapeutic use of (90)Y-IT in low-grade FL. Methods Medical records of patients with low-grade FL (WHO grade 1-2) who received treatment with (90)Y-IT at Mayo Clinic Cancer Center between January 2003 and December 2018 were analyzed. Overall response rate (ORR) and complete response rate (CR) were calculated. Progression-free survival (PFS), time to next therapy (TTNT), and overall survival (OS) were analyzed using the Kaplan-Meier method. Results Our cohort consists of 137 patients - 29% (40/137) with UFL and 71% (97/137) with RFL. The median age at diagnosis was 60 years (range, 18-86) with 54% (74/137) males. The median number of previous treatments in RFL patients was 1 (range, 1-5). ECOG performance status at the time of treatment was 0 in 90% and 1 in 10% of patients. 87% (119/137) had stage III/IV disease at the time of (90)Y-IT therapy. The median follow up from the time of (90)Y-IT therapy was 10.2 years (95% CI; 8.8, 11.6); 69% (95/137) of patients are alive. The ORR was 100% in UFL with 93% (37/40) CR while ORR in UFL was 93% (90/97) with 73% (71/97) CR. 45% (48/108) of the CR patients remain in continuous CR (CCR) with a median follow-up of 7 years (95% CI; 5.2, 9.9). CCR was observed in 55% (22/40) of UFL patients compared to 27% (26/97) of RFL patients. 63% (86/137) of patients had relapsed. More relapses occurred in the RFL group (69/97; 71%) compared to the UFL group (17/40; 43%), (p=0.002). In the entire cohort, the median PFS was 2.5 years (95% CI; 2.1, 3.5) and TTNT was 3.6 years (95% CI; 2.5, 4.7). Median PFS was significantly higher in UFL group compared to RFL group- 4.1 years (95% CI; 2.3, NR) vs 2.2 years (95% CI; 1.6, 3.1), respectively (Figure 1-A). Median TTNT was higher in UFL group compared to RFL group- NR (95% CI; 4.1 years, NR) vs 2.4 years (95% CI; 2, 3.6), respectively (Figure 1-B). Median OS (entire cohort) was 18 years (95% CI; 15.8, NR) with no statistically significant difference between UFL group and RFL group; NR (95% CI; NR, NR) vs 18 years (95% CI; 12.3, 20.5), respectively (Figure 1-C). Transformation to high grade lymphoma was seen in 19% (18/97) in RFL group compared to 2.5% (1/40) in UFL group, (p=0.005). Median time to transformation was 4.3 years (range, 1-11). More patients developed therapy-related myelodysplastic syndrome/acute myeloid leukemia (MDS/AML) in the RFL group 14% (14/97) compared to 2.5% (1/40) in the UFL group (p= 0.02). Median time to develop MDS/AML was 3.3 years (range, 0-9.7). Grade ³3 neutropenia was observed in 46% of patients with median time to recovery of 21 days (range, 2-706). Grade ³3 thrombocytopenia was observed in 47% of patients with median time to recovery of 23 days (range, 7-548). Eighteen patients required growth factors support and 14 required transfusions. Non-hematologic AEs included mild to severe fatigue in 35 patients. Conclusion Radio-immunoconjugate therapy with (90)Y-IT is an effective single-agent regimen for low-grade FL. The response and survival data in this large real-world cohort is superior to the pivotal trials of this agent conducted nearly 20 years ago. The data in untreated FL is also of interest and provides the rationale for our current randomized phase 2 trial in untreated FL (https://clinicaltrials.gov/show/NCT02320292). Long-term complete remission (>7 years) was seen in 35% of the study population. Based on these promising results, clinical trials combining RIC with novel agents that could potentiate its effects are warranted. Figure 1 (A) Progression-free survival; comparing time to progression or death after (90)Y-IT treatment between previously untreated patients (UFL) and patients with relapsed/refractory FL (RFL), (B) Time to next therapy; comparing time to starting next line of treatment after (90)Y-IT treatment between UFL and RFL, (C) Overall survival; comparing time to death from all causes after (90)Y-IT treatment between UFL and RFL. Figure 1 Disclosures Tun: DTRM Biopharma: Research Funding; TG Therapeutics: Research Funding; BMS: Research Funding; Curis: Research Funding; Celgene: Research Funding; Mundi-pharma: Research Funding. OffLabel Disclosure: Yttrium-90 ibritumomab tiuxetan [(90)Y-IT; Zevalin] is a radio-immunoconjugate (RIC) which targets CD20. It is approved in relapsed/refractory low-grade NHL and as consolidation after upfront induction chemoimmunotherapy for FL. We are discussing its use as a frontline therapy in low grade FL.

Abstract Introduction: Ibritumomab tiuxetan (Zevalin¨) is a radioimmunoconjugate agent that targets CD20-expressing B cell lymphomas. Currently, it is the only radioimmunoconjugate agent available on the market and is FDA approved for relapsed/refractory follicular lymphoma (FL). A retrospective study of patients with low grade FL (WHO grade 1 and 2) treated with ibritumomab tiuxetan at Mayo Clinic Florida from 2000 to 2016 was performed. Methods: The patient population consisted of previously untreated as well as relapsed low grade FL. We evaluated patient characteristics, response rate, duration of response, progression free survival, overall survival and time to next treatment. Previously untreated patients were treated with ibritumomab tiuxetan due to ineligibility for standard chemotherapy and prolonged immunotherapy, or their preference. Comparison between previously untreated FL patients treated with ibritumomab tiuxetan as the first line of treatment versus patients with relapsed FL treated with ibritumomab tiuxetan as second, third or fourth line therapy was made. Results: Low grade FL patients (n=41) that received ibritumomab tiuxetan were identified; 13 patients (32%) with previously untreated FL and 28 patients (68%) with relapsed FL. The data on response to treatment is presented in Table 1. Ibritumomab tiuxetan use in previously untreated FL was associated with more complete responses than in the relapse setting (92% vs 50% at 6 months, p=0.036). Previously untreated FL patients that received ibritumomab tiuxetan as first line therapy had better progression free survival (80% vs 35% at 3 years). Ibritumomab tiuxetan use in relapsed FL was associated with significant shorter time to relapse compared to previously untreated FL (median 1.3 years vs 4.8 years, p=0.017, figure 1) and shorter time to next treatment (65% at 4 years compared to 0% in previously untreated, p=0.007). 15% of newly diagnosed FL treated with ibritumomab tiuxetan relapsed compared to 64% of relapsed FL patient. There was no significant difference in overall survival between the two groups. The incidence of grades 3-4 neutropenia (Absolute Neutrophil Count <1000 x109/L), Anemia (Hb <8 g/dL) and Thrombocytopenia (Platelets <25 x109/L) were 47%, 7.7% and 48.7% respectively. Only 6/41 patients (15%) had cytopenias that required transfusion of blood products. More significant cytopenias were seen in relapsed group compared to previously untreated group. Conclusions: Ibritumomab tiuxetan as first line treatment in previously untreated FL patients at our institution was associated with improved response rate, better progression free survival and shorter time to next treatment when compared to its use in relapsed FL. Ibritumomab tiuxetan has significant therapeutic efficacy for both previously untreated as well as relapsed low grade FL. It was well tolerated without significant treatment-related morbidity or mortality. Moreover, treatment schedule was very convenient for the patients. Our results suggest that treatment with ibritumomab tiuxetan is an effective option for those previously untreated low grade FL patients who cannot take standard chemoimmunotherapy. Disclosures No relevant conflicts of interest to declare.

Abstract PURPOSE: Preoperative stereotactic radiosurgery (SRS) for symptomatic brain metastases has arisen as a therapeutic option for patients with brain lesions, potentially reducing radionecrosis risk, leptomeningeal disease risk, as well as delays in systemic therapy after craniotomy. The purpose of our work is to analyze the current evidence regarding 1-year local control (LC) and RN rates in the preoperative and postoperative settings. METHODS AND MATERIALS: Population, Intervention, Control, Outcomes, Study Design/Preferred Reporting Items for Systematic Reviews and Meta-analyses and Meta-analysis of Observational Studies in Epidemiology guidelines were used to select articles in which patients had “large” brain metastases (&gt;4 cm3 or &gt;2 cm in diameter) solely treated with preoperative or postoperative SRS and 1-year LC and/or rates of RN reported. Radiosurgery was stratified by timing: preoperatively or postoperatively. Random effects meta-analyses using timing of SRS relative to surgery as covariates were conducted. Meta-regression and Wald-type tests were used to determine the effect of increasing tumor size on the summary estimate, where the null hypothesis was rejected for p &lt; 0.05. RESULTS: Fifteen studies were included (of 314 screened), published between 2012 and 2018 with 854 brain metastases. Preoperative SRS was delivered in 229 lesions. The 1-year LC random effects estimate was 79.1% (95% confidence interval [CI]: 55.9–95.0%; I 2 = 80%) for preoperative SRS and 80.5% (95% CI: 66.3–91.5%; I 2 = 93%) for postoperative SRS (p=0.9). Radionecrosis incidence random effects estimate was 2.1% (95% CI: 0.1–8.6%; I 2 = 36%) for preoperative SRS and 6.3% (95% CI: 1.1–15.4%; I 2 = 90%) for postoperative SRS (p=0.52). CONCLUSIONS: Rates of 1-year LC and RN incidence are similar after preoperative SRS as compared to postoperative SRS for large brain metastases. Results from ongoing prospective clinical trials studying preoperative SRS are important to further investigate these two techniques.