Two B or not two B; the question of bendamustine dosing in low grade lymphoma.

Background: Follicular lymphoma (FL) is an indolent yet incurable B-cell lymphoma subtype commonly treated with a combination of bendamustine and anti-CD20 antibodies such as rituximab. While the standard administration involves a 2-day dosing schedule, the COVID-19 pandemic prompted the exploration of a 1-day regimen to reduce hospital visits for immunocompromised patients. This study aimed to compare the efficacy and safety of 1-day versus 2-day bendamustine regimens. Methods: We conducted a retrospective analysis of 144 patients with FL, marginal zone lymphoma, mantle cell lymphoma, or Waldenström macroglobulinemia treated at the Department of Internal Medicine and Hematology, Semmelweis University between 2015 and 2023. All patients received bendamustine combined with either rituximab or obinutuzumab. The primary endpoint was progression-free survival (PFS); secondary endpoints included overall survival (OS) and toxicity. Kaplan-Meier survival analysis and appropriate statistical tests were applied. Results: The median PFS for the cohort was 69.47 months; OS was not reached. Despite receiving a significantly lower cumulative dose, and being significantly older, patients on the 1-day regimen had similar PFS (not reached vs. 69.47 months; p = 0.885) and no significant difference in OS (p = 0.147) compared to the 2-day group. Adverse events were more frequent in the 2-day regimen group, including severe side effects, such as neutropenia (p = 0.044). Conclusion: A 1-day bendamustine regimen may offer comparable efficacy to the standard 2-day schedule, with a potentially more favorable toxicity profile and better convenience, especially in older or more vulnerable patient populations. These findings warrant further investigation in prospective randomized trials to establish optimal dosing strategies.