Rituximab therapy in Waldenstrom's macroglobulinemia: preliminary evidence of clinical activity.

To assess the preliminary efficacy of rituximab therapy in Waldenstrom's macroglobulinemia (WM), we examined the clinical and laboratory data for all patients with WM treated on IDEC Pharmaceuticals sponsored trials and one patient treated at Walter Reed Army Medical Center. Seven symptomatic patients with WM were treated with four (n = 6) or eight (n = 1) weekly infusions of rituximab (375 mg/m2). Patients had received a median of three prior therapies (range 1-4) which included alkylator therapy in all (five patients refractory) and fludarabine in four (all refractory). Therapy was tolerated well in all patients without decrement in cellular immune function or significant infectious morbidity. Partial responses were noted in three of these patients, including two with fludarabine-refractory disease. The median progression-free survival for these patients was 6.6 months (range 2.2-29+ months). These data suggest that rituximab has clinical activity in heavily pre-treated patients with Waldenstrom's macroglobulinemia. Based on these data, clinical studies of Rituximab in previously untreated and treated WM appear indicated.