Michallet, Anne‐Sophie

Introduction Venetoclax + rituximab resulted in a 2-year progression-free survival estimate of 85% in the mostly 2nd-line, post-chemotherapy setting of the MURANO clinical trial (Seymour NEJM 2018). Short remissions with venetoclax in patients (pts) with prior cBTKi treatment (tx) for CLL are reported. However, these cohorts have included heavily pre-treated pts. Here, we report outcomes with venetoclax-based regimens in a contemporary cohort with cBTKi-exposed CLL and no prior chemotherapy. Methods We conducted a retrospective study of pts who received venetoclax for relapsed CLL after prior cBTKi tx at Mayo Clinic and across 8 centers in France. Pts with any prior chemotherapy tx were excluded. Pts were grouped as cBTKi-resistant (CLL disease progression on cBTKi) and cBTKi-exposed (any prior cBTKi tx but without disease progression). Overall survival (OS) was analyzed as the time from initiation of venetoclax until date of death or last known to be alive. Time to next therapy or death (TTNTD) after venetoclax was defined as the time from venetoclax initiation until the earliest date of next tx or death. Cox proportional hazards regression models were used to estimate associations of factors with OS and TTNTD. Results A total of 85 pts received venetoclax, including: venetoclax monotherapy (n=13, 15%), venetoclax + rituximab (n=45, 53%), and venetoclax + obinutuzumab (n=27, 32%). Patient characteristics at the time of venetoclax start were as follows: median age 69 years (interquartile range [IQR] 62-77), 59 (69%) male, 45% (33/73 evaluated) with TP53 disruption (del(17p) or TP53 mutation), 82% (46/56 evaluated) with unmutated IGHV, and 41% (15/37 evaluated) with complex karyotype (CK; ≥3 clonal structural or numerical abnormalities on karyotype). The median prior lines of therapy was 1 (IQR 1, 2); 32 (38%) pts had received prior anti-CD20 monoclonal antibody and 8 (9%) pts had received 2 prior cBTKi. Prior cBTKi tx was stopped for a reason other than disease progression in 46 (54%) pts (cBTKi-exposed) and due to CLL progression in 39 (46%) pts (cBTKi-resistant). TP53 disruption, unmutated IGHV, and CK were more common in the cBTKi-resistant subgroup. Among pts with cBTKi-resistant CLL, 60% (12/20 evaluated) had a BTK and/or PLCG2 mutation. Median follow-up from start of venetoclax-based therapy was 20 months. The median TTNTD and OS for the entire cohort was 36 (95% CI 29-not evaluable [NE]) and 68 (95% CI 39-NE) months, respectively. Among the 46 pts with cBTKi-exposed CLL, the median duration of prior cBTKi tx was 6.7 months (IQR 1.8, 23.7). The median TTNTD and OS from venetoclax start were both 78 months in pts with cBTKi-exposed CLL. The 24-month TTNTD and OS estimates were 73% and 81%, respectively. Among the 39 pts with cBTKi-resistant CLL, the median duration of prior cBTKi tx was 42.3 months (IQR 23.4, 60.1). The median TTNTD from venetoclax start in pts with cBTKi-resistant CLL was 30 months. The 24-month TTNTD estimate was 65% in the cBTKi-resistant subgroup, 53% with venetoclax monotherapy (n=5), 62% with venetoclax + rituximab (n=30), and 100% venetoclax + obinutuzumab (n=4). The median OS from venetoclax initiation was 39 months overall in pts with cBTKi-resistant CLL. The 24-month OS estimate was 84% in the cBTKi-resistant subgroup overall, 53% with venetoclax monotherapy, 87% with venetoclax + rituximab, and 100% with venetoclax + obinutuzumab. On a univariate analysis in the whole cohort, only TP53 disruption was associated with shorter TTNTD (HR 2.23; 95% CI 1.02-4.87; P=0.04) and only older age was associated with shorter OS (HR 1.05; 95% CI 1.007-1.095, P=0.02). On a univariate analysis in the cBTKi-resistant subgroup, only TP53 disruption was associated with shorter TTNTD (HR 6.68; 95% CI 1.51-29.46; P=0.01) and OS (HR 7.95; 95% CI 1.02-61.97; P=0.04). Duration of prior cBTKi exposure (as a continuous variable) was not associated with survival outcomes in the cBTKi-resistant subgroup. Conclusions Pts with chemotherapy-naïve, cBTKi-treated CLL had worse than expected outcomes with venetoclax-based tx in a mostly 2nd-line tx cohort, particularly pts with cBTKi-resistant CLL. The frequency of high-risk disease features, shorter duration of disease control with their initial cBTKi tx, and small cohort size warrant caution in generalizing these results to all pts with cBTKi-resistant disease. Novel tx trial strategies in 1st- and 2nd-line settings remain a high priority for high-risk pts.

Abstract INTRODUCTION Central nervous system (CNS) relapse is a challenging situation in diffuse large B-cell lymphoma (DLBCL). High CNS-International Prognostic Index (IPI), activated B-cell (ABC) subtype and MYD88 L265P mutation, features often found in transformed Waldenström macroglobulinemia (WM), are associated with a higher risk for developing CNS relapse. This study was aimed to describe CNS involvement in a large cohort of transformed WM. METHODS This international multicenter retrospective study included patients with a diagnosis of WM and a concurrent or sequential histological diagnosis of DLBCL. CNS disease was diagnosed by detection of DLBCL cells in the cerebrospinal fluid and/or by brain biopsy. Patients with CNS involvement by lymphoplasmacytic cells (Bing-Neel syndrome) were excluded. Of 254 identified patients with a diagnosis of histological transformation (HT) between 1988 and 2020, 19 were excluded due to lack of data on extranodal involvement. The first part of the analysis focused on baseline CNS involvement. Clinicobiological characteristics were compared between groups using Chi-square or Fisher's exact tests or Mann Whitney tests as appropriate. We analyzed CNS recurrence in the second part of the study. Forty-eight additional patients were excluded due to baseline CNS involvement (n = 25), absence of treatment at HT (n = 14) and lack of details on follow-up (n = 9). Cumulative incidence of CNS relapse was analyzed using competing-risk models that accounted for other events like systemic relapse or death from any cause, reporting sub-hazard ratio (SHR). RESULTS Baseline CNS involvement was present in 25 patients (11%) with transformed WM, including 10 (4%) with parenchymal disease, 10 with leptomeningeal, 4 (2%) with both, and 1 with unspecified CNS involvement. Characteristics associated with baseline CNS involvement were performance status 2-4 (P=0.03) and ≥2 extranodal sites (P=0.02). Median survival after HT was 1 year [0.7-2.5], comparable to the one of patients without CNS disease (1.8 year [1.2-2.6], P=0.74). We observed no difference in survival based on isolated CNS involvement (n = 10) compared to CNS and systemic involvement (n = 15) (P=0.94). Twenty-three CNS relapses occurred (12%). The 2-year and 3-year rates of CNS relapse were 9% (95% CI, 6-14) and 11% (95% CI, 7-16) (Figure 1). The median time to relapse in the CNS was 11 months (95% CI, 7-25). Thirteen CNS recurrences (57%) occurred during the first year of follow-up. Seventy percent were isolated CNS relapses. The location was leptomeningeal in 43% of cases, parenchymal in 35%, both in 17%, and unspecified in 4%. According to CNS-IPI risk groups (data available for 20 patients), 9 patients (45%) belonged to the high-risk group, 10 (50%) to the intermediate-risk group and 1 (5%) to the low-risk group. Prior to CNS relapse, 87% of patients had received rituximab, and 39% had received CNS prophylaxis (30% intrathecal chemotherapy, 4% high-dose methotrexate (HD-MTX), and 4% both). After CNS recurrence, 96% of patients received salvage treatment: combination of HD-MTX and HD-cytarabine (48%), HD-MTX alone (30%), or HD-cytarabine alone (9%). Four patients underwent consolidative autologous stem cell transplantation. The median survival after CNS relapse was 5.6 months. Factors associated with 3-year cumulative incidence of CNS recurrence in univariate analysis were involvement of kidney/adrenal glands (HR, 4.4; P=0.01) and MYD88 L265P mutation (P=0.01) (Figure 2A and B). Of note, among 74 patients (over 187, 40%) with data available for MYD88 mutation status, 11 CNS relapses occurred in patients with MYD88 L265P mutation (n = 54, 20%) whereas no relapse were observed in MYD88 WT cohort (n = 20). A trend toward higher risk of CNS relapse for ≥2 extranodal sites (HR, 2.3, 95% CI 0.98-5.3; P=0.06) was observed. Cumulative incidence according to CNS-IPI risk groups (0% in the low-risk, 9% in the intermediate-risk and 14% in the high-risk group) was not statistically significant (P=0.47). CONCLUSION CNS involvement occurs frequently in transformed WM. Rate of CNS relapse seems similar to DLBCL patients belonged to the CNS-IPI high-risk group. Special attention should be paid to patients with kidney/adrenal involvement and MYD88 L265P mutation. Figure 1 Figure 1. Disclosures Vos: Sanofi: Membership on an entity's Board of Directors or advisory committees; Celgene: Other: Travel reimbursement. Treon: X4: Research Funding; Janssen: Consultancy, Research Funding; Dana Farber Cancer Institute: Current Employment; BMS: Consultancy, Research Funding; Self: Patents & Royalties: Holder of multiple patents related to testing and treatment of MYD88 and CXCR4 mutated B-cell malignancies; AbbVie: Consultancy, Research Funding; BeiGene: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding. Dimopoulos: Janssen: Honoraria; Beigene: Honoraria; Amgen: Honoraria; BMS: Honoraria; Takeda: Honoraria. Kapoor: Cellectar: Consultancy; Karyopharm: Consultancy; BeiGene: Consultancy; Pharmacyclics: Consultancy; Sanofi: Consultancy; Amgen: Research Funding; Ichnos Sciences: Research Funding; Regeneron Pharmaceuticals: Research Funding; Glaxo SmithKline: Research Funding; Karyopharm: Research Funding; Sanofi: Research Funding; Takeda: Research Funding; AbbVie: Research Funding. Castillo: Abbvie: Consultancy, Research Funding; BeiGene: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; Janssen: Consultancy; Roche: Consultancy; TG Therapeutics: Research Funding.

Abstract Background: One of the main complications in CLL is Richter syndrome (RS). RS derives from the rare transformation of chronic lymphocytic leukemia (CLL) into an aggressive lymphoma, most commonly of the diffuse large B-cell lymphoma (DLBCL) type. RS occurs in 2.2% to 8% of patients with CLL and the prognostic is poor with a median survival from 5 to 8 months. Detection of RS by imaging has resulted in conflicting and non-significant results. Aim: The objective of this study was to validate recent findings correlating FDG/PET imaging and histological features in CLL and to demonstrate that a tumoral maximum standardized uptake value > 10 measured on 18F-FDG-PET is a new valid marker to discriminate RS. Results: From June 2006 through December 2012, 240 patients from the Division of hematology of Centre Hospitalier Lyon Sud and Créteil and from the Mayo Clinic Rochester have been analyzed with a mean age of 62 years (21-91). Clinical, histological (confirm by biopsy) and biological parameters have been identified with 10% of the patients as having RS, 34% stable CLL disease; 42% of rapid CLL progression (histological features of progression defined as increased large cell number, large confluent proliferation centers or high proliferation rate assessed by Ki-67 but not meeting criteria for diffuse large B-cell lymphoma/RS) and 14% with others diseases (e.g. infection and or cancers). For patients with stable CLL disease, the median tumoral SUV max was 2 (range: 0-2.4). Among patients with a rapid progression of CLL, 90% had a tumoral SUV max <10 but greater than the liver median SUV max (4.5 range: 1-11). In contrast, 90% of patients with RS had a median tumoral SUV max >10 (12.9; range: 5-27). A statistically significant difference between SUV max of CLL patients with stable disease and RS was observed (2.2 vs. 12.9; p< 0.0001) and similarly for SUV max of CLL patients with rapid disease progression and RS (4.5 vs 12.9; p< 0.0001). Regardless of the RS prevalence (2.2% to 8%), statistical tests identified a threshold of tumor SUV max > 10 as the more discriminating cut off. Using this threshold, the sensitivity and specificity of PET to identify RS in our cohort are 91% and 95% respectively. Assuming an RS prevalence of 2.2%, positive predictive value (PPV) and negative predictive value (NPV) using the >10 threshold were 28.7% and 99.8%; for an 8% prevalence of RS, the PPV and NPV are 60.8 and 99.2% respectively.The proportion of correctly classified patients with RS is more accurate using a threshold of tumoral SUV max > 10 than 5 (2.2% RS prevalence: 94.8% versus 71.8%; 8% RS prevalence: 94.6% versus 73.5%). Finally analysis of the area under the curve (AUC) reveals a value of 0.95 (95% confidence interval: 0.89- 0.99). Recently, Falchi et al, reported on 332 patients with CLL classified as 95 RS, 117 rapid progression and 120 stable disease and demonstrated a strong correlation between histological features and PET imaging. A SUV max ≥10 strongly correlated with a shorter overall survival. Similarly, in our study we have shown excellent sensitivity and negative predictive value estimated at 100%, revealing the ability of 18F-FDG-PET-CT to rule out the diagnosis of RS if the tumor SUV max is less than 10. Conclusion: 18F-FDG-PET-CT is a valuable tool in the diagnostic evaluation of RS for patients with CLL. It is not only useful to identify RS syndrome and guide the site of biopsy but also to identify CLL patients who will experience more rapid disease progression. An SUV max > 10 is the optimal threshold to distinguish RS in CLL. Disclosures No relevant conflicts of interest to declare.

Abstract Abstract 3925 Introduction: CLL patients (pts) who relapse following purine-analog or bendamustine-based treatments have a poor prognosis. These pts have limited therapeutic options and novel agents with alternative mechanisms of action are needed. Several phase 1 and 2 trials in rel/ref CLL showed promising activity with escalating dose regimens of lenalidomide (LEN). In other phase II studies improved clinical responses to lenalidomide appeared to correlate with dose levels > 5mg/day. This phase 2 trial investigates the safety of LEN initiated at 3 different starting doses followed by a step-wise dose escalation as tolerated in rel/ref CLL. Methods: In this ongoing trial, eligible pts with rel/ref CLL who have received ≥ 1 prior treatment regimen containing purine-analog or bendamustine are being enrolled. The objectives of this study are to evaluate primarily the safety and secondarily the efficacy of different LEN dose regimens. Pts are randomized 1:1:1 to receive a double-blinded starting dose of 5 mg, 10 mg, or 15 mg oral LEN on days 1–28 of each 28-day cycle. In all 3 treatment arms, the dose is escalated by 5 mg increments every 28 days to reach a maximum dose of 25 mg/d, depending on tolerability. In instances of poor tolerability, dose reductions also occur in 5 mg steps. Pts are stratified by relapsed versus refractory status to their last purine-analog or bendamustine-based treatment regimen and according to age (< 65 vs ≥ 65 years). Tumor lysis syndrome (TLS) prophylaxis comprises of oral hydration and allopurinol 300 mg/day and is initiated ≥ 3 days prior to starting study drug and for a minimum of the first 3 treatment cycles. A total of 105 pts are planned for enrollment to the study. Per protocol, unblinded interim analyses were conducted by the independent Data Monitoring Committee (DMC) after 18 subjects completed 1 cycle and continue at 13-week intervals. Results: To date, 95 pts are enrolled at a median age of 64 years (range 32–81). Enrolled pts are primarily male (67%) and Caucasian (92%). Cytogenetic data are available for 73 pts; 21% have del(17p), 55% have del(13q), 25% have del(11q), and of 72 patients evaluable for trisomy 12, 11 patients (15%) tested positive. IGVH is unmutated in 77% of 77 evaluable pts and 44% of 84 evaluable pts are ZAP70-positive. Based on the Binet and Rai staging systems 9 (10%), 25 (26%) and 24 (25%) of subjects are stage A, B and C, respectively; 7 (7%), 12 (13%) and 16 (17%) subjects are low, intermediate or high-risk disease, respectively. For 2 (2%) subjects the Binet/Rai staging is currently unknown. Overall, 19 pts (20%) received prior bendamustine-containing treatment and 71 pts (75%) received prior fludarabine-based treatment. The median number of prior therapies was 3 (range 1–10). Most common hematological grade ≥ 3 AEs include neutropenia (62%) and thrombocytopenia (34%). At baseline, 19% of pts presented with grade 1–2 neutropenia. The most common non-hematological ≥ grade 3 AEs include pneumonia (13%), tumor flare (13%), and fatigue (11%). TLS was reported in 3 pts (3%): grade 1, 3, and 4. In total, 8 grade 5 events were reported, 3 of which were suspected to be related to LEN: 2 cases of pneumonia and 1 death for unknown cause. At the time of the cut-off, 59 pts (62%) have discontinued treatment. Most common reasons for treatment discontinuation include disease progression (n = 20) and AEs (n = 20). To date, 47 pts (49%) have dose escalated above their starting dose levels of which 12 patients escalated to the highest dose level (25 mg daily). 18 subjects have had no dose level reduction or escalations and 1 patient is still in the first cycle of the study. Average duration of treatment is 6.5 cycles, and median number of cycles is 4. Efficacy evaluations are completed monthly after 3 months of study drug treatment. At time of the data reporting, 5 pts were on study drug but did not reach the first assessment at cycle. For the 90 pts evaluable for response, the investigator's assessment indicates 2 pts (2%) reached CR, 36 (40%) achieved PR, 33 (37%) patients had SD, and 19 (21%) pts progressed. Conclusion: The independent DMC, as of 14 June, 2012 (N=95), recommended that accrual into all three treatment arms should continue as planned, suggesting all three starting doses were well tolerated. To date, the ORR is 42% and 49% of pts were dose escalated at least once. In this rel/ref CLL population LEN appears active, and completion of accrual will clarify the appropriate dose at which to initiate therapy. Disclosures: Wendtner: Celgene Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; GSK: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Mundipharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Off Label Use: use of lenalidomie in relapsed/refractory CLL. Hallek:Celgene Corporation: Consultancy, Honoraria, Research Funding. Hillmen:Celgene Corporation: Honoraria. Gregory:Celgene Corporation: Honoraria, Research Funding. Stilgenbauer:Celgene Corporation: Honoraria, Research Funding, Speakers Bureau. Kipps:Celgene Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Purse:Celgene Corporation: Employment, Equity Ownership. Zhang:Celgene Corporation: Employment, Equity Ownership. Mei:Celgene Corporation: Employment.