Durable Responses with Bendamustine Monotherapy In Patients with Relapsed/Refractory Indolent B-Cell Non-Hodgkin Lymphoma (B-NHL) and Mantle-Cell Lymphoma (MCL): Updated Follow-up Data From a Japanese Multicenter Phase II Study
Authors: Itoh Kuniaki , Ando Kiyoshi , Ogura Michinori , Ishizawa Kenichi , Watanabe Takashi , Uike Naokuni , Terui Yasuhito , Usuki Kensuke , Nagai Hirokazu , Uoshima Nobuhiko , Kubota Nobuko , Ohmachi Ken , Uchida Toshiki , Yamamoto Joji , Choi Ilseung , Tobinai Kensei 
Published: October 2019

Abstract
Abstract 4884

Background:
Bendamustine is an alkylating agent with a unique mechanism of action and has demonstrated efficacy as a single agent for the treatment of relapsed or refractory indolent B-NHL or MCL. We conducted a multicenter, phase II study of bendamustine in Japanese patients with indolent B-cell NHL or MCL, reporting an overall response rate of 91% (90% in indolent B-NHL and 100% in MCL) according to International Workshop Response Criteria after a median follow-up of 12.6 months (Ohmachi et al. Cancer Sci 2010 [Epub ahead of print]). Here we report the updated progression-free survival (PFS) data, including median PFS, which had not been reached at the time of previous reports.

Patients and Methods:
Eligible patients (aged 20–75 years; Eastern Cooperative Oncology Group performance status of 0 or 1) with measurable, pathologically confirmed indolent B-NHL or MCL that failed to respond to, or relapsed after, prior therapy were enrolled. Bendamustine 120 mg/m2 was administered intravenously over 60 minutes on days 1 and 2 every 21 days for up to 6 cycles. PFS was assessed 3 months after completion of the last cycle, and then at 3-month intervals.

Results:
A total of 69 patients, aged 33–75 years, were enrolled: 58 with indolent B-NHL, mainly follicular lymphoma (n = 52), and 11 with MCL. Patients had primarily stage III or IV disease. The median number of prior regimens was 2 (range, 1–9) for patients with indolent B-NHL and 4 (range, 1–16) for those with MCL. A median of 5 (range, 1–6) bendamustine cycles were administered, with 72% of patients completing 3 or more cycles. The median follow-up time for all patients is 20.6 months (range, 2.5–27.2 months). The median PFS was 21.1 months (95% CI, 15.8-NA; NA = not available due to short period of observation): 20.0 months (95% CI, 12.3-NA) in indolent B-NHL, and 21.7 months (95% CI, 16.5-NA) in MCL. Estimated 2-year PFS rates were 45.2% and 34.1% in indolent B-NHL and MCL, respectively.

Conclusions:
Bendamustine monotherapy is highly effective in patients with relapsed or refractory indolent B-NHL and MCL. The durable responses observed in this study strongly support the use of bendamustine in these patients and are particularly encouraging in the relapsed or refractory MCL population.

Disclosures:
Off Label Use: Bendamustine is a novel alkylator that has shown efficacy and safety in patients with indolent lymphomas, and particularly encouraging is the activity in patients with mantle cell lymphoma, which is difficult to treat. Although bendamustine is currently investigational in Japan, approval for relapsed/refractory indolent NHL and mantle cell lymphoma is anticipated in October 2010.