Chimeric Anti-CD20 Monoclonal Antibody (Rituximab; Mabtheraâ) in Remission Induction and Maintenance Treatment of Relapsed /Resistant Follicular Non-Hodgkin’s Lymphoma : A Phase III Randomized Intergroup Clinical Trial.

Background. In view of a) the efficacy of Rituximab (R) monotherapy in relapsed low grade lymphoma; b) the feasibility to combine R with cytostatic drugs c) the potential of such combinations to clear minimal residual disease, in 1999 we started a phase III clinical trial in patients with relapsed follicular non-Hodgkin’s lymphoma, with 2 main objectives. First: to compare CHOP and R-CHOP as to response rate and response quality. Second: to establish the effect of maintenance treatment with R on progression-free survival (PFS ).

Study design. Patients with stages III or IV follicular lymphoma at initial diagnosis and relapsed after or resistant to a maximum of two non-anthracycline containing systemic chemotherapy regimens, were randomized to remission induction with either 6 cycles of standard CHOP (once every 3 weeks) or CHOP + R (375 mg /m² at day 1 of each cycle of CHOP). Those with a complete or partial remission after 6 cycles of therapy underwent a second randomization to no further treatment or maintenance treatment with R (375 mg/m² once every 3 months until relapse or for a maximum period of two years).

Results. In February 2004, a preplanned second interim analysis by the IDMC was performed. At that time 461 patients had been included. Of these, 369 could be evaluated for response (188 CHOP; 181 R-CHOP). The groups did not differ as to age, sex, performance status, time from initial diagnosis, number and type of, and best overall response to prior chemotherapy. Both treatment arms yielded similar PR rates: CHOP 53.7%; R-CHOP 52.5 %. However, there was a highly significant difference in CR rates: CHOP 18.1% versus R-CHOP 30.4 % (p=0.0004). 319 patients have been randomized for maintenance treatment. Of these, 268 were evaluable (132 observation; 136 R maintenance). 1 year and 3 year PFS were 54.9% and 31.2% respectively in the observation arm, and 80.2 % and 67.7% in patients with R maintenance treatment (p< 0.0001). There is as yet no impact on OS: the observed difference (in favor of R maintenance) was not significant for an interim analysis (p=0.03). There were no differences in toxicity between CHOP and R-CHOP induction treatments. Maintenance treatment was associated with minimal toxicity. Because the planned second interim analysis revealed that the primary endpoints for both the induction and maintenance part of the study had been reached, the formal criteria for stopping the trial have now been met.

Conclusion. In patients with relapsed/resistant follicular lymphoma R-CHOP remission induction results in a highly significant increase in CR rate as compared to CHOP. Moreover, this is the first trial to show that in these patients Rituximab maintenance treatment achieves a considerable improvement in PFS.