The chimeric human-mouse anti-CD20
monoclonal antibody rituximab has durable single-agent activity in patients with relapsed and refractory indolent
non-Hodgkin's lymphoma. The focus of this report is a phase II trial evaluating the efficacy of single-agent
rituximab as first-line
therapy in patients with indolent
lymphoma and scheduled maintenance treatment in prolonging duration of remission. Patients received a 4-week course of standard
rituximab (375 mg/m(2) intravenously weekly x 4). Those achieving objective response or stable disease then received maintenance courses of standard
rituximab every 6 months, for a maximum of four
rituximab courses. Of 62 patients entered in the trial, 61% had
follicular lymphoma while 39% had
small lymphocytic lymphoma (SLL). At 6 weeks, 28 of 60 evaluable patients (47%) had an objective response. The response rate improved to 73% (37% complete response) following maintenance
rituximab therapy and was similar in patients with
follicular lymphoma and SLL (76%
v 70%, respectively). Median progression-free survival for the entire group was 34 months. Single-agent
therapy was well tolerated and maintenance
rituximab was administered without grade 3/4 toxicity. Because of the higher activity of
rituximab in this study compared with previous results in patients with relapsed or refractory SLL, a second phase II trial of identical design but limited to patients with SLL and
chronic lymphocytic leukemia was initiated. Forty-four patients entered this second trial and, at present, 27 continue to receive maintenance courses of
rituximab. The current response rate is 56% (8% complete responses). In summary,
rituximab appears highly active as first-line single-agent
therapy for indolent
non-Hodgkin's lymphoma and responses may be improved with maintenance courses of
rituximab. Results suggest a higher response rate to
rituximab when used as first-line compared with second/third-line treatment, particularly in the subset of patients with SLL and
chronic lymphocytic leukemia. Further follow-up will provide important information regarding the impact of first-line and maintenance
rituximab on progression-free survival in patients with indolent
non-Hodgkin's lymphoma.