Impact of Rituximab On the Treatment of Waldenström's Macroglobulinemia (WM).

Rituximab was first approved by the FDA for use in relapsed and/or refractory low grade or follicular B cell non-Hodgkin's lymphoma in 11/1997. Since that time it has been widely used in WM, and is the backbone of drug combinations developed for treatment of this disease.

To evaluate the impact of rituximab on overall survival (OS), we retrospectively evaluated patients (pts) treated at our center who received primary therapy for symptomatic WM with combinations of either alkylating agents (AA), nucleoside analogs (NA) +/− AA, or bortezomib (B), each with or without rituximab (R). The effect of primary therapy on OS was compared between patients receiving primary therapy before and after rituximab use for WM began at our center (11/11/1998). OS was calculated from the date of initial treatment until date of death or last follow-up. Due to small patient numbers, those who received vincristine-doxorubicin-dexamethasone (2 pts), single agent rituximab (3 pts), or rituximab-alkylating agent combinations (11 pts) as primary therapy, were excluded from the analysis.

Among 315 patients with previously untreated symptomatic WM treated since 3/1966, 118 received AA alone; 137 received NA +/− AA alone (85 pts) or with R (52 pts), and 44 received B + R. Median age, hemoglobin, platelet count and β2 microglobulin were comparable between all treatment groups (AA alone, NA +/− AA alone, NA +/− AA + R, B + R). Only median albumin differed significantly, with levels of 3.7 g/dL (AA alone), 4.1 g/dL (NA+/− AA alone), 4.3 g/dL (NA+/− AA + R) and 4.4 g/dL (B + R), respectively (p < 0.01). The median OS of pts treated with AA was 4.5 years, and 6.5 years with NA +/− AA, while the median OS of pts treated with NA+/− AA + R (median follow-up: 8 years) and B + R (median follow-up: 2.6 years) has not been reached. Comparing all patients treated with vs. without R, median OS is >13 years vs. 5.6 years (p<0.01).

While pts with WM have most certainly benefitted from improvements in supportive care and the greater availability of salvage therapy options in the modern era, the addition of rituximab to available therapies appears to have significantly improved the OS of patients with WM compared with AA or NA +/− AA alone. Our data supports the role of rituximab as an indispensable component of modern therapy for this disease.

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No relevant conflicts of interest to declare.