Bendamustine and rituximab (BR) versus dexamethasone, rituximab, and cyclophosphamide (DRC) in patients with Waldenström macroglobulinemia.

The treatment approaches for Waldenstrom macroglobulinemia (WM) are largely based upon information from single-arm phase II trials, without comparative data. We compared the efficacy of two commonly used regimens in routine practice (bendamustine-rituximab (BR) and dexamethasone, rituximab plus cyclophosphamide (DRC)) and evaluated their activity with respect to the patients' MYD88L265P mutation status. Of 160 consecutive patients, 60 received BR (43 with relapsed/refractory WM) and 100 received DRC (50 had relapsed/refractory WM). In the treatment-naïve setting, overall response rate (ORR) was 93% with BR versus 96% with DRC (p = 0.55). Two-year progression-free survival (PFS) with BR and DRC was 88 and 61%, respectively (p = 0.07). In salvage setting, ORR was 95% with BR versus 87% with DRC, p = 0.45; median PFS with BR was 58 versus 32 months with DRC (2-year PFS was 66 versus 53%; p = 0.08). Median disease-specific survival was not reached with BR versus 166 months with DRC (p = 0.51). The time-to-event endpoints and depth of response were independent of the MYD88 mutation status. Grade ≥ 3 adverse events of both regimens were comparable. A trend for longer PFS was observed with BR although the regimens have comparable toxicities. The activity of BR and DRC appears to be unaffected by patients' MYD88 mutation status.