This phase II trial investigated the safety and efficacy of retreatment with rituximab(Drug information on rituximab) (Rituxan) in patients with low-grade or follicular non-Hodgkins lymphoma who relapsed following a response to rituximab therapy. A total of 60 patients received 375 mg/m² of rituximab every week × 4 doses (intravenous [IV] infusion). Of the 60 patients, 5% had lymphomas classified as International Working Formulation (IWF) A; 45%, IWF B; 47%, IWF C; and 3%, IWF D. All patients had received at least two prior therapies and at least one prior course of rituximab.
Most adverse experiences were transient and grade 1 or 2. Significant myelosuppression was not observed; hematologic toxicity was generally mild and reversible. All patients remained CD20 positive, and none developed human antichimeric antibody (HACA). The type, frequency, and severity of adverse events were not apparently different from those reported in other rituximab studies.
The overall response rate (ORR) in 57 evaluable patients was 40%. Medians for time to progression (TTP) in responders and duration of response (DR) have not been reached; Kaplan-Meier estimates are 16.7+ months (range, 3.7+ to 25.1 months) and 15.0+ months (range, 5.4 to 26.6 months), respectively, and are longer than the medians achieved in these patients prior course of rituximab (TTP and DR of 12.4 and 9.8 months, respectively). Responses are ongoing in 6 of 23 responders.
CONCLUSION: This study shows that patients can be treated safely and effectively with multiple courses of rituximab without induction of human antichimeric antibody (HACA) and without the myelosuppression common after multiple courses of chemotherapy. In this retreated population, safety and efficacy were not apparently different than are seen following initial rituximab exposure.