Cheah, Chan Y.

PURPOSE The combination of the Bruton tyrosine kinase inhibitor ibrutinib with bendamustine-rituximab for first-line treatment of mantle cell lymphoma (MCL) prolonged progression-free survival (PFS), but without improvement in overall survival (OS), likely because of toxicity. Acalabrutinib was shown to be efficacious and less toxic than ibrutinib in a head-to-head trial in chronic lymphocytic leukemia and therefore might lead to better outcomes in MCL. METHODS Patients 65 years and older with previously untreated MCL received acalabrutinib (100 mg twice daily) or placebo (until disease progression or unacceptable toxicity), plus six cycles of bendamustine (90 mg/m 2 once daily; days 1 and 2) and rituximab (375 mg/m 2 as a single dose; day 1) followed by rituximab maintenance in responding patients for 2 years. Crossover to acalabrutinib at disease progression was permitted. The primary end point was PFS per the independent review committee; overall response rate and OS were secondary end points. RESULTS In total, 598 patients were randomly assigned, with 299 in each arm. At a median follow-up of 49.8 months using the reverse Kaplan-Meier method, the median PFS was 66.4 months in the acalabrutinib arm and 49.6 months in the placebo arm (hazard ratio [HR], 0.73 [95% CI, 0.57 to 0.94]; P = .0160). Benefit was seen across all subgroups, including those with high-risk features. Overall response/complete response rates were 91.0%/66.6% and 88.0%/53.5% in the acalabrutinib and placebo arms, respectively. OS was not significantly different (HR, 0.86 [95% CI, 0.65 to 1.13]; P = .27). Grade 3 or greater adverse events were reported in 88.9% and 88.2% in the acalabrutinib and placebo arms, respectively. CONCLUSION The combination of acalabrutinib with bendamustine-rituximab significantly improved PFS. Clinical benefit of acalabrutinib with bendamustine-rituximab was achieved with manageable toxicity.

Background: Positron emission tomography (PET) scan is the imaging modality of choice for initial staging and response assessment of follicular lymphoma (FL). Quantitative parameters such as standardized uptake value (SUV) have been investigated as putative prognosticators in FL, with high baseline SUVmax predicting aggressive disease. To date, there is no data to guide treatment choices in patients (pts) with high SUVmax but with no documented evidence of histologic transformation (HT). Specifically, it remains unclear whether anthracycline-containing regimens, such as R-CHOP, are more beneficial than R-Bendamustine (BR) in these pts. Therefore, we aimed to compare the efficacy of frontline R-CHOP and BR in newly diagnosed FL pts based on the SUVmax at baseline PET (bPET). Patients and Methods: Pts with newly diagnosed, biopsy-proven FL1-2 and FL3A who had a bPET scan and who received either first-line R-CHOP or BR within 6 months of diagnosis between 2002 and 2022 were evaluated. Analysis was restricted to pts with age < 70 years to reduce confounding of age with treatment selection. Cohorts included were the FOLL12 (n=562, Luminari et al JCO 2022) and the R-chemotherapy arm of the RELEVANCE (n=216, Morschhauser et al NEJM 2018) clinical trials, the prospectively enrolled Molecular Epidemiology Resource (MER) and the Lymphoma Epidemiology of Outcomes (LEO) cohorts (n=288) and a retrospective cohort from 13 Australian centers (n=219). Choice of chemotherapy regimen was per treating physician. Maintenance was per protocol (FOLL12/RELEVANCE) or per treating physician (MER/LEO/Australia). Event-free survival (EFS) and overall survival (OS) were defined as time from treatment initiation to progression, relapse, retreatment or death; both were censored at 72 months due to varying follow-up across cohorts. SUVmax was grouped by tertile within each cohort to account for potential differences in SUVmax distributions and patient populations across cohorts. Kaplan Meier curves and multivariable Cox models cohort-stratified and adjusted for clinical factors (FLIPI, ECOG PS, age, grade 3A) were used to evaluate outcomes. Results: The median age at diagnosis was 57 years (IQR 49-64). 651 (51%) pts were treated with R-CHOP and 634 (49%) with BR. Within the study cohorts, there was a prevalence of cases receiving BR compared to R-CHOP in the Australian (90% vs 10%) and MER/LEO (68% vs 32%) cohorts, while the opposite was observed in the RELEVANCE (16% vs 84%) and FOLL12 (37% vs 63; p<0.001) trials. Pts receiving R-CHOP were slightly younger (median 56 vs 58 years, p=0.005), more frequently had grade 3A (17% vs 7%, p<0.001), elevated LDH (27% vs 22%, p=0.029), bulky disease > 7 cm (44% vs 37%, p=0.019), lower ECOG PS (PS >1 7% vs 13%, p<0.001), and higher rate of high risk FLIPI (37% vs 30%, p=0.005). Baseline SUVmax was slightly lower in R-CHOP (median 10.7, IQR 7.9-14.9) vs BR (median 11.0, IQR 8.2-14.2) treated pts (p=0.0045). At a median follow-up of 56 months (range, 1-72 months), 415 pts (32%) had an event and 103 (8%) died. Higher SUVmax was not associated with EFS (middle tertile HR=0.96, 95% CI 0.76-1.22; upper tertile HR=0.86, 95% CI 0.68-1.09; p=0.45) or OS (middle tertile HR=1.28, 95% CI 0.80-2.05; upper tertile HR=0.97, 95% CI 0.59-1.59; p=0.44) in multivariable models stratified on cohort and adjusted for treatment and clinical factors. We then compared outcomes by treatment within tertiles of SUVmax. In multivariable models, R-CHOP had modestly inferior EFS to BR in low (HR=1.27, 95% CI 0.84-1.93) and middle tertiles (HR=1.49, 95% CI 0.99-2.25), and modestly superior OS to BR in low (HR=0.59, 95% CI 0.23-1.47) and middle (HR=0.79, 95% CI 0.37-1.71) tertiles. Both EFS (HR=1.06, 95% CI 0.71-1.58) and OS (HR=1.02, 95% CI 0.45-2.30) for R-CHOP were similar to BR in the highest tertile. No comparisons identified a statistically significant benefit for either therapy in multivariable models when evaluating SUVmax tertile subsets. Conclusions: In this large multicenter study of newly diagnosed FL pts with bPET who received frontline immunochemotherapy, higher baseline SUVmax was not associated with inferior outcomes after adjusting for treatment and clinical factors. Within the caveats of retrospective studies and confounding of treatment selection, these data provide no clear insights for SUVmax-based therapy selection in first-line follicular lymphoma pts treated with immunochemotherapy.

Background: Splenic marginal zone lymphoma (SMZL) is a rare indolent disease with a median overall survival (OS) of more than 10 years, although a proportion of patients may develop aggressive histology transformation. In a previous report from this large, international dataset, the 10-year cumulative incidence of transformation was 17% (95% 13-21) and in another study of 186 patients, the 10-year cumulative incidence was 14%Click or tap here to enter text.. In this report, we focus on risk factors for transformation as well as clinical characteristics and outcomes of transformed SMZL (tSMZL). Patients and methods: Adults diagnosed with SMZL in 2000-2018 were identified through regional or nationwide population-based registries or from hospital registries. Only patients likely to have SMZL as defined by Matutes et al. were included. Those with discordant lymphoma and/or transformation at diagnosis were excluded. Medical records were reviewed by local clinicians with experience in hematology/oncology, and detailed information on clinical characteristics, treatment lines, and outcomes was collected. Only histologically confirmed high-grade transformations (HT) were included. OS was defined as the time from transformation to death or censoring at last follow-up. Additional analyses stratified by treatment exposure prior to HT and treatment of HT were conducted. Multivariable Cox analyses were performed to determine clinicopathological features associated with transformation and OS. Results: Out of 940 patients with SMZL, 111 developed HT during a median follow-up of 9.1 years. The median time from diagnosis to HT was 3.4 years with an interquartile range of 1.6-7.4 years. Median age at HT was 71 years. Patients with HT shared similar baseline characteristics to those without in terms of age at diagnosis (66.4 vs 67.6), f:m ratio (1.5 vs 1.1) and ECOG ³2 (7.2% vs 7.4%). The 5-yr OS from the time of HT was 42% (CI 95%, 32-54). Of the 111 patients with tSMZL, a complete treatment history from SMZL diagnosis until HT was available for 88 included in the following analyses. By the time of HT, 46 had not received any prior systemic therapy (37 only splenectomy, 9 no therapy), 6 patients had received rituximab alone or combined with splenectomy, and 36 patients had received chemotherapy alone or as part of combined modality treatment. In a uni- and multivariable models for HT, we assessed age, treatment at diagnosis, sex, extra-hilar lymphadenopathy, and extranodal involvement. In both the uni- and multivariable model, age >70 (HR 1.9, 95% CI: 1.1-3.4), immediate treatment including splenectomy (HR 2.0, 95% CI: 1.05-3.6), and extra-hilar lymphadenopathy (HR 1.9, 95% CI: 1.1-3.3) were associated with higher HT hazard, while extranodal involvement (HR 0.23, 95% CI: 0.06-0.84) was associated with a lower HT hazard. At the time of first-line treatment, multivariable analysis revealed similar results and with no association between risk of transformation and treatment strategy (i.e splenectomy alone, rituximab monotherapy or chemotherapy with /without rituximab or splenectomy, and other). At the time of HT, patients who had been previously treated with chemotherapy had an inferior 5-year OS of 24% (95%CI: 13-44%) versus 54% (95%CI: 41-71%) for those who had not received chemotherapy prior to HT. In contrast, there was no difference in the survival of patients that transformed less than or more than 24 months from diagnosis with 5-year OS after HT of 35% (95%CI 20-60%) and 45% (95%CI, 33-61%) respectively. In a multivariable Cox regression analyses of age at time of HT, sex, time since last treatment <24 months, chemo-exposure in previous treatment lines and anthracycline-containing therapy (+/-R) at the time of HT, only prior chemo-exposure was borderline associated with poorer OS (HR 1.8, 95%CI: 0.9-3.5). Conclusion: Patients with SMZL face a notable risk of developing tSMZL over time. Patients in need of immediate treatment at first SMZL diagnosis, age >70 and extrahilar lymphadenopathy had a higher risk of tSMZL and outcomes at the time of HT were poor if patients had been exposed to prior chemotherapy after adjustment for age, sex, and time since last treatment.

Introduction: The primary analysis of the phase 3 ECHO trial (NCT02972840) demonstrated that acalabrutinib plus bendamustine-rituximab (ABR) significantly improved progression-free survival (PFS) vs placebo plus bendamustine-rituximab (PBR) in older patients (pts) with previously untreated mantle cell lymphoma (MCL) (Wang et al. EHA 2024, Abstract #LB3439). Here we present additional efficacy and safety results from the ECHO trial. Methods: Pts aged ≥65 years (y) with previously untreated MCL and ECOG PS ≤2 were randomly assigned 1:1 to receive ABR or PBR. Acalabrutinib (100 mg twice daily) or placebo was administered until progressive disease (PD) or unacceptable toxicity. Induction with BR was administered for 6 cycles followed by rituximab maintenance (A±R maintenance, cycles 7-30) in pts achieving a partial or complete response (PR or CR). Pts progressing on PBR could cross over to receive acalabrutinib monotherapy. PFS (primary endpoint) was assessed by independent review committee. Minimal residual disease (MRD) negativity rate (10-5) was assessed in peripheral blood (every 24 weeks [wks], at CR, and at PD) and bone marrow (at CR) by NGS-based ClonoSEQ assay (Adaptive Biotechnologies). Results: Among the 598 pts randomized to ABR or PBR (299 in each arm), high-risk baseline characteristics included high-risk simplified MIPI score in 24.1% and 24.4%, blastoid histology in 8.7% and 6.7%, pleomorphic histology in 5.0% and 6.0%, centrally tested Ki-67 ≥30% in 46.5% and 49.2%, and known TP53 mutation in 7.4% and 9.7%, respectively. PFS hazard ratios (HRs) for subgroups were 0.78 (95% confidence interval [CI] 0.51-1.19) in pts with high-risk simplified MIPI score, 0.68 (95% CI 0.29-1.58) in pts with blastoid histology, 0.64 (95% CI 0.25-1.66) in pts with pleomorphic histology, 0.69 (95% CI 0.49-0.98) in pts with Ki-67 ≥30%, and 0.88 (95% CI 0.42-1.78) in pts with known TP53 mutation. In the ABR arm, median PFS was 22.2 months (mo) among pts who discontinued acalabrutinib during induction for reasons other than PD or death, 29.4 mo in pts who discontinued acalabrutinib during A±R maintenance (cycles 7-30) for reasons other than PD or death, and not reached in pts who received acalabrutinib for 31 cycles or more. Among evaluable patients who were MRD negative at the end of induction (24 wks), the rate of conversion to MRD positive during maintenance was lower in the ABR arm (5.85%; n=11/188) than in the PBR arm (15%; n=26/171). Conversely, among evaluable pts who were MRD positive at the end of induction (24 wks), 37.5% (n=3/8) in the ABR arm and 20% (n=3/15) in the PBR arm converted to MRD negative during maintenance. Overall rates of AEs were similar in each arm during induction, but were higher in ABR during A±R maintenance (cycles 7-30) and more so in the monotherapy phase (cycle 31+). Grade ≥3 TEAEs (ABR vs PBR) were 70.0% vs 68.7% during induction, 64.9% vs 62.9% during A±R maintenance (cycles 7-30), and 57.0% vs 45.3% during monotherapy (cycle 31+). Similarly, rates of TEAEs leading to discontinuation of acalabrutinib/placebo were 8.1% vs 8.8% during induction, 23.9% vs 19.0% during A±R maintenance (cycles 7-30), and 25.9% vs 13.7% during monotherapy (cycle 31+). Exposure-adjusted incidence rates per 100 person-years reduced the difference between ABR and PBR for clinically relevant TEAE rates (32.6 vs 29.3 for grade ≥3 serious TEAEs; 4.2 vs 4.0 for grade 5 TEAEs; 15.5 vs 12.4 for TEAEs leading to acalabrutinib/placebo discontinuation), possibly due to longer median exposure to acalabrutinib (28.6 vs 24.6 mo). Conclusion: Acalabrutinib in combination with BR provides a significant PFS benefit in pts with previously untreated MCL, including those with high-risk features. Furthermore, the addition of acalabrutinib to BR provided a greater PFS effect among pts in the ABR arm with the longest exposure to acalabrutinib. The PFS improvement may be partially driven by the contribution of acalabrutinib to sustained MRD-negative status and deepened responses after the end of induction. ABR provides this clinical benefit without excess toxicity as shown by attenuated differences between arms in exposure-adjusted incidence rates, suggesting that higher AE rates in the ABR arm are likely due in part to the longer duration of acalabrutinib treatment vs placebo. These data emphasize the benefits of acalabrutinib in frontline MCL treatment in high-risk pts and the additional benefit of continuous therapy.

Introduction: Bruton tyrosine kinase (BTK) inhibitors are highly effective against Waldenström macroglobulinemia (WM). Their effectiveness can be limited by resistance caused by BTK mutations and intolerance. BGB-16673 is a bivalent small molecule that induces BTK degradation by binding specifically to BTK and the E3 ligase. The E3 ligase catalyzes the transfer of ubiquitin molecules to BTK, which marks BTK for destruction by the proteasome. Preclinically, BGB-16673 degraded wild-type and mutant BTK associated with covalentand noncovalent BTK inhibitors (ncBTKis), leading to tumor suppression. CaDAnCe-101 (BGB-16673-101; NCT05006716) is an ongoing, open-label, first-in-human, phase 1/2 study evaluating BGB-16673 monotherapy in patients with a range of B-cell malignancies. Here, early results in patients with WM enrolled in the phase 1 portion are presented. Methods: Eligiblepatients must have confirmed R/R WM (≥2 prior therapies), an ECOG performance status of 0-2, and adequate organ function. Patients must have previously received an anti-CD20 antibody and, in the US and EU, a covalent BTK inhibitor (cBTKi). BGB-16673 was orally dosed once daily in 28-day cycles. Dose escalation used a Bayesian optimal interval design (6 planned dose levels, 50-600 mg once daily). Primary objectives were to evaluate safety/tolerability (CTCAE v5.0) and to establish the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D). Dose-limiting toxicities (DLTs) were assessed in the first 4 weeks (cycle 1). A secondary objective was to evaluate the overall response rate (ORR, IWWM-6 consensus criteria), with the first assessment occurring after 4 weeks of treatment. Results: As of May 24, 2024, 22 patients with WM were enrolled and treated (100 mg, n=4; 200 mg, n=10; 350 mg, n=8). The median age was 73.0 (range, 56-81) years, and the median number of prior therapies was 3.5 (range, 2-11), including prior cBTKis (n=22 [100%]), BCL2 inhibitors (n=4 [18%]), and ncBTKis (n=3 [14%]). Twenty patients (91%) had previously received chemotherapy. According to the International Prognostic Scoring System for WM, 6 patients (27%) had low-risk disease, 7 (32%) had intermediate-risk disease, and 8 (36%) had high-risk disease (missing/unknown data, n=1). Five patients (23%) had BTK mutations, 20 (91%) had MYD88 mutations, and 8 (36%) had CXCR4 mutations. The median follow-up was 4.3 (range, 0.3-21.3) months. Ninety-five percent of patients reported any-grade treatment-emergent adverse events (TEAEs; grade ≥3, 45%; serious, 23%), the most common (≥20%) of which were neutropenia/neutrophil count decreased (32%; grade ≥3, 23%), contusion (23%; no grade ≥3), and diarrhea (23%; no grade ≥3). The most common grade ≥3 TEAE (≥20%) was neutropenia/neutrophil count decreased. No atrial fibrillation, hypertension, febrile neutropenia, or major hemorrhage occurred. Three patients (14%) had a grade ≥3 infection (bronchopulmonary/cerebral aspergillosis, septic shock, and pseudomonal bacteremia/sinusitis). No patients had a TEAE that led to treatment discontinuation or dose reduction. No DLTs occurred, and the MTD was not reached. One patient (5%) died due to a TEAE (septic shock, considered related to disease progression). One patient died due to disease progression. In 21 response-evaluable patients (1 too early), the ORR (minor response or better) was 90%, the major response rate (partial response [PR] or better) was 81%, and the very good PR or better rate was 14%. Median time to first response was 0.95 (range, 0.9-3.7) months, with responses deepening over time. Seventeen patients remain on treatment and have ongoing responses. Responses were seen at the lowest dose (100 mg, 4/4), in patients previously treated with a cBTKi (19/21) and an ncBTKi (3/3), and in patients discontinued from prior BTKi due to disease progression (15/17). In addition, responses were observed in patients with and without mutations in BTK (with, 5/5; without, 6/8; unknown, 8/8), MYD88 (with, 18/20; without, 1/1), and CXCR4 (with, 8/8; without, 11/13). One patient had IgM flare at initial response assessment and went on to develop PR. Conclusions: Early data from this ongoing, first-in-human study demonstrate that the novel BTK degrader BGB-16673 has a tolerable safety profile and shows promising antitumor activity in heavily pretreated patients with BTK inhibitor-exposed R/R WM, including those with BTK and CXCR4 mutations.

PURPOSE Nodular lymphocyte–predominant Hodgkin lymphoma (NLPHL) is a rare cancer, and large international cooperative efforts are needed to evaluate the significance of clinical risk factors and immunoarchitectural patterns (IAPs) for all stages of pediatric and adult patients with NLPHL. METHODS Thirty-eight institutions participated in the Global nLPHL One Working Group retrospective study of NLPHL cases from 1992 to 2021. We measured progression-free survival (PFS), overall survival (OS), transformation rate, and lymphoma-specific death rate. We performed uni- and multivariable (MVA) Cox regression stratified by management to select factors for the lymphocyte-predominant international prognostic score (LP-IPS) validated by five-fold cross-validation. RESULTS We identified 2,243 patients with a median age of 37 years (IQR, 23-51). The median follow-up was 6.3 years (IQR, 3.4-10.8). Most had stage I to II (72.9%) and few B symptoms (9.9%) or splenic involvement (5.4%). IAP was scored for 916 (40.8%). Frontline management included chemotherapy alone (32.4%), combined modality therapy (30.5%), radiotherapy alone (24.0%), observation after excision (4.6%), rituximab alone (4.0%), active surveillance (3.4%), and rituximab and radiotherapy (1.1%). The PFS, OS, transformation, and lymphoma-specific death rates at 10 years were 70.8%, 91.6%, 4.8%, and 3.3%, respectively. On MVA, IAPs were not associated with PFS or OS, but IAP E had higher risk of transformation (hazard ratio [HR], 1.81; P < .05). We developed the LP-IPS with 1 point each for age ≥45 years, stage III-IV, hemoglobin <10.5 g/dL, and splenic involvement. Increasing LP-IPS was significantly associated with worse PFS (HR, 1.52) and OS (HR, 2.31) and increased risk of lymphoma-specific death (HR, 2.63) and transformation (HR, 1.41). CONCLUSION In this comprehensive study of all ages of patients with NLPHL, we develop the LP-IPS to identify high-risk patients and inform upcoming prospective clinical trials evaluating de-escalation of therapy for patients with low LP-IPS scores (<2).

Background:Richter transformation (RT) occurs in up to 10% of patients with chronic lymphocytic leukemia (CLL), typically presents as an aggressive diffuse large B-cell lymphoma (DLBCL) and is associated with poor survival. RT has no approved standard therapy; and clinical trial enrollment is the preferred first line of therapy. Pirtobrutinib, a highly selective, non-covalent (reversible) BTKi, that inhibits both wildtype and C481-mutant BTK with equal low nM potency, has favorable oral pharmacology that enables continuous BTK inhibition throughout the dosing interval. Pirtobrutinib demonstrated durable overall response rates (ORR) and was well tolerated in patients (pts) with poor-prognosis B-cell malignancies regardless of prior therapy. Here we provide updated safety and efficacy of pirtobrutinib in RT pts from the phase 1/2 BRUIN trial (NCT03740529). Methods: Pts with previously treated, histologically confirmed RT were eligible in the global, multicenter, phase 1/2 BRUIN study. Pts with untreated RT became eligible after Amendment 10. All but one patient received the recommended phase 2 dose of 200 mg daily. Key endpoints included investigator-assessed ORR, DoR per Lugano 2014 criteria, OS, and safety. A data cut of 05 May 2023 was utilized. To assess clonal relationship, IGH rearrangement studies were done on tissue biopsies with RT involvement, and baseline blood or bone marrow (BM) samples with CLL involvement. Results: Among all pts with RT (N=82) the median age was 67 (range, 26-95) and the median total number of lines of prior systemic therapy was 4 (range, 0-13). Pts with prior treatment had a median of 2 CLL-directed therapies and 2 RT-directed therapies. Eight pts did not have a previous line of RT-directed therapy, and 1 patient received neither RT- nor CLL-directed therapy. Common prior RT- and CLL-directed therapies (RT, CLL) included: chemotherapy (76%, 52%), cBTKi (34%, 62%), anti-CD20 antibody (78%, 66%), BCL2i (38%, 49%), stem cell transplant (SCT; 6%, 7%), and CAR-T (11%, 4%). Of 29 pts with bone marrow screening, 41.4% had CLL alone present in BM, 13.8% had DLBCL present and 24.1% had both CLL and DLBCL present. For 39 pts with available PET data, the median SUVmax was 19.1 (range, 2.6-41.2). For all 82 pts, the ORR was 50.0% (95% CI, 38.7-61.3) including complete (13.4%, n=11) and partial (36.6%, n=30) responses. For 61 pts who received prior cBTKi therapy, the ORR was 45.9% (95% CI 33.1-59.2). Among 28 pts with an RT-directed cBTKi and 51 pts with prior CLL-directed cBTKi, the ORR was 42.9% (95% CI, 24.5-62.8) and 43.1% (95% CI, 29.3-57.8), respectively. In 50 pts who discontinued prior cBTKi due to disease progression, the ORR was 42.0% (95% CI, 28.2-56.8). At median follow-up time of 9.7 months, the median DoR for all 82 RT pts was 7.4 months (95% CI, 3.1-19.1) and the estimated rate at 12 months was 45.9% (95% CI, 28.3-61.8). The median time on treatment for the 41pts who responded to treatment was 8.3 months. Eight pts stopped pirtobrutinib to pursue curative-intent allogeneic SCT and DoR was censored at the last preceding disease assessment. At a median survival follow-up of 18.3 months, the median OS for the entire RT cohort was 12.5 months (95% CI, 6.9-20.5). At 18 months, the OS rate was 44.3% (95% CI, 32.5-55.4). Frequent treatment-emergent adverse events (TEAE) in the RT cohort (n=82) were neutropenia/decreased neutrophil count (29.3%, n=24), fatigue (24.4%, n=20) and diarrhea, dyspnea, thrombocytopenia, and pyrexia (18.3% each, n=15). Common grade ≥3 TEAEs were neutropenia/decreased neutrophil count (23.2%, n=19), thrombocytopenia (11.0%, n=9), plus anemia and sepsis (9.8% each, n=8). Any grade hypertension (3.7%, n=3) or atrial fibrillation (1.2%, n=1) were infrequent. Three pts (3.7%) had treatment-related AEs leading to dose reductions, but no pt had a treatment-related AE leading to pirtobrutinib discontinuation. Analyses of clonality will be presented. Conclusions: Continued follow-up from BRUIN demonstrates encouraging response and OS in pts with RT. Pirtobrutinib remains well-tolerated with low rates of discontinuation and manageable safety profile. While RT remains a challenging diagnosis, pirtobrutinib represents a potential treatment option that warrants further investigation.

Introduction: Splenic marginal zone lymphoma (SMZL) is a rare, indolent disease. There is no universally accepted standard therapy and long-term outcome data are limited. Rituximab monotherapy is increasingly used over splenectomy in the first-line setting despite a paucity of comparative studies. In the absence of randomized trials, large-scale international real-world data studies are critical to evaluate outcomes of different treatment interventions and to understand the natural history of SMZL in the rituximab-era. Methods: Adult patients with SMZL diagnosed between Jan 1 st 2000 and Dec 31 st 2018 were identified using regional/nationwide population-based registries or hospital registries in Europe, the UK, North America, and Australia. Medical records and pathology reports from eligible patients were reviewed locally by clinicians with specialty experience in hemato-oncology. SMZL cases were required to meet the diagnostic criteria by Matutes et al. Detailed data on clinico-pathological features, comorbidities, treatments (including treatment intention), treatment responses and survival outcomes were entered in a central study database. Overall survival (OS) was defined as time from diagnosis until death from any cause or censoring at last follow-up unless stated otherwise. Event-free survival (EFS) was defined as the time from diagnosis until histological transformation, initiation of new chemotherapy or death from any cause. Survival probabilities were estimated using the Kaplan-Meier estimator. Cumulative risk of transformation was estimated with death as a competing risk. Primary endpoints were 10-year OS and 5-year EFS respectivly. Results: A total of 934 patients from 25 sites were included. Median age at diagnosis was 68 years (IQR 60-76) and 54% were female. Bone marrow involvement was present in 96% (564/590) of those assessed, anemia (Hb &lt;12g/dL for women or &lt;13g/dL for men) in 58%, LDH &gt;UNL in 46%, lymphocytosis (&gt;5 x10 9/L) in 34%, and B-symptoms in 34%. Treatment data were available for 97% of patients. Median follow-up was 9.1 years (range 0-23). Watch and wait was the initial strategy in 28% and 88% of patients received at least one line of treatment during follow-up with the most common being splenectomy (45%), immuno-chemotherapy (19%) or rituximab monotherapy (8%). Fifteen percent received “other” treatments (i.e., combinations of listed therapies and/or radiation). The overall response rate to first-line treatment was 88% (95%CI: 85-90%) with 61% (95%CI: 57-64%) achieving CR. Second line (2L) therapy was needed in 34% during follow-up, 3L in 20% and 4L+ in 9%. The 5-year EFS and OS for all patients were 61% (95%CI: 57-65%) and 77% (95%CI: 74-80%) respectively. The 10-year OS and lymphoma-specific mortality (with non-SMZL deaths as competing risk) estimates were 60% (95%CI: 57-64%) and 11% (95%CI: 9-14%) respectively. The 5-year OS after 2L and 3L were 61% (95%CI: 55-68%) and 51% (95%CI: 42-61%) respectively (figure 1). The 10-year cumulative risk of histological transformation was 17% (95%CI: 13-21%), with 5-year post-transformation OS of 42% (32-54%). At the time of transformation, 60% were chemo-naive and 52% had never been treated for SMZL. The 5-year OS for chemo-naive patients with transformation was 54% (95%CI: 41-71%) versus 24% (95% CI: 13-44%) for transformations after (immuno)chemotherapy (p = 0.01). When comparing patients intended for treatment in first line with splenectomy (n=312) versus rituximab (n=70), patients treated with splenectomy more frequently presented with extra-hilar lymphadenopathy (35% vs 18%), splenomegaly (92% vs 87%) and anemia (64% vs 48%). OS was similar for the two groups (Figure 2, p = 0.53). The 5-year EFS were 63% (95%CI: 57-68%) and 64% (95%CI: 54-77%), respectively (p = 0.31). Conclusions: To date, this is the largest real-world study of SMZL with detailed treatment and outcome data. The study shows that histological transformation was not uncommon with 10-year risk of 17%. However, outcomes for the entire cohort were excellent irrespective of initial treatment and both OS and EFS were similar after first line rituximab versus splenectomy. Long-term survival remained relatively high even following multiple lines of therapy.