Combined rituximab, bendamustine, and dexamethasone chemotherapy for relapsed or refractory indolent B-cell non-Hodgkin lymphoma and mantle cell lymphoma: a multicenter phase II study

This multicenter phase II study (UMIN000008145) aims to investigate the efficacy and safety of six cycles of combination therapy (RBD) comprising rituximab, bendamustine, and dexamethasone (DEX) for relapsed or refractory (RR) indolent B-cell non-Hodgkin lymphoma (B-NHL) and mantle cell lymphoma (MCL). Although the initial study protocol comprised 20mg/body DEX on days 1 and 2, and 10mg/body on days 3-5 [high-dose (HD-) DEX group], the dose of DEX was later decreased to 8mg/body on days 1 and 2 [low-dose (LD-) DEX group] due to frequent cytomegalovirus (CMV) antigenemia and recurrent retinitis. We enrolled 33 patients, and LD-DEX and HD-DEX were administered in 15 and 18 patients, respectively. The overall response and the 3-year progression-free survival rates were 88% and 75.5%, respectively. The leading adverse event was myelosuppression. Incidence of grade 3-4 leukocytopenia, neutropenia, and lymphocytopenia was 55%, 67%, and 91%, respectively. The most frequent nonhematological adverse events were CMV antigenemia and rash (33% and 30%, respectively). Incidence of CMV antigenemia over 10/100,000 white blood cells was significantly lower with LD-DEX than that with HD-DEX (P=0.0127). In conclusion, RBD showed significant effectiveness for RR indolent B-NHL and MCL.