Higher incidence of thrombocytopenia during obinutuzumab plus bendamustine therapy for untreated follicular lymphoma: a retrospective analysis by the Okayama Hematology Study Group.

Progression-free survival in patients with untreated follicular lymphoma (FL) has significantly improved with obinutuzumab plus chemotherapy followed by obinutuzumab maintenance, compared with rituximab plus chemotherapy. However, the survival outcome and adverse event profile in Japanese FL patients treated with obinutuzumab plus bendamustine (GB) therapy are not well investigated. Recently, we encountered some cases of grade 3-4 thrombocytopenia during GB therapy in patients with FL. This retrospective multicenter survey aimed to identify the characteristics of patients who received GB therapy and developed thrombocytopenia. A total of 54 patients with FL treated by GB therapy between August 2018 and December 2020 were investigated. After a median follow-up of 12.6 months, thrombocytopenia of any grade was observed in 48 (88.9%) patients, including 9 (16.7%) patients with grade 3-4 thrombocytopenia. Notably, although eight of nine patients with grade 3-4 thrombocytopenia were female, no patient characteristics (including gender) were significantly associated with grade 3-4 thrombocytopenia. Importantly, grade 3-4 thrombocytopenia frequently occurred in the first GB therapy cycle, which suggests that platelet count should be monitored carefully in patients who have just started GB therapy.