Pb2317: Polatuzumab Vedotin Plus Bendamustine and Rituximab Therapy in Relapsed or Refractory Diffuse Large B-Cell Lymphoma: A Single-Institution Experience Focusing on Detailed Assessment of Toxicities

Topic: 19. Aggressive Non-Hodgkin lymphoma - Clinical Background: Polatuzumab vedotin combined with bendamustine and rituximab (pola-BR) therapy has shown efficacy for patients with relapsed or refractory diffuse large B cell lymphoma (DLBCL) in several clinical trials. However, few studies have reported efficacy and detailed evaluation of adverse events (AEs) of pola-BR therapy in clinical practice. Aims: To evaluate in detail the efficacy and toxicity of pola-BR therapy for patients with relapsed or refractory DLBCL in clinical practice. Methods: We retrospectively analyzed 28 consecutive patients who were treated with pola-BR therapy for relapsed or refractory DLBCL between 2021 and 2022 in our institution. The primary objective was assessment of toxicities due to pola-BR therapy including toxicity type, frequency, grade, time of onset, and duration. Efficacy analyses, such as response, duration of response, and survival, were also evaluated. This study was approved by the Institutional Review Board of the Japanese Foundation for Cancer Research. Results: The median age was 73.5 years (range: 44-85), and 19 patients (68%) were over 70 years old. Among the 28 patients, there were 15 males (54%) and 13 females (46%). Fifteen patients (54%) had histologic transformation from low-grade lymphoma, eight patients (29%) had non-GCB type DLBCL, four patients (14%) had GCB type DLBCL, and one patient had high-grade B-cell lymphoma with MYC and BCL2 rearrangements. Thirteen patients (46%) had received four or more regimens of prior therapy, and one patient had been previously treated with CAR T-cell therapy. Nine patients (32%) were refractory to the last prior therapy and 17 patients (61%) received pola-BR therapy within 6 months of their last therapy. Twenty-seven patients (96%) received prophylaxis for pneumocystis infection and herpes zoster. The median number of cycles of pola-BR therapy was four (range: 1-6), and five patients (18%) completed six cycles. The main reasons for discontinuation of pola-BR therapy were disease progression in seven patients (25%) and AEs in nine patients (32%; four had cytomegalovirus (CMV) infection, two had skin rash, one had myelosuppression, one had deep vein thrombosis, and one had varicella-zoster virus infection). The common AEs and the timing of onset (percentage, median, range) were peripheral neuropathy in eight patients (29%, 45 days, 10-219), CMV infection in seven patients (25%, 63 days, 8-131), diarrhea in seven patients (25%, 85 days, 1-131), fever in six patients (21%, 24 days, 3-46), pruritus in six patients (21%, 34 days, 1-47), and skin rash in four patients (14%, 29 days, 5-38) (Figure). The overall response rate was 54% (15 patients, including 14 complete metabolic response patients). The median duration of response was 383 days (95% CI, 128-NA). The median progression-free survival was 329 days (95%CI, 166-NA), and the median overall survival was not reached, with a median follow-up duration of 194 days (29-678). There were nine deaths (seven had disease progression, one associated with CMV infection, and one for another reason). Summary/Conclusion: Our findings suggest that Pola-BR therapy is an effective treatment option in mainly elderly patients with heavily pretreated relapsed or refractory DLBCL. However, 32% of patients discontinued treatment due to AEs. In particular, CMV infection was frequently observed (25%) with a wide range of durations of onset. Our findings also suggest that appropriate safety management for pola-BR therapy is necessary, including paying attention to CMV infection.