Rituximab Maintenance Treatment for a Maximum of 5 Years in Follicular Lymphoma: Final Results of the Randomized Phase III Trial SAKK 35/03

Background: Follicular lymphoma is usually a disase with a prolonged course and a chemotherapy-free regimen might be a favourable treatment strategy. SAKK 35/03 investigated two different durations of rituximab maintenance (5 years vs. 6 months) in patients with follicular lymphoma after induction with 4 weekly doses of rituximab monotherapy. With a median follow-up of 6.4 years we were not able to show a benefit with long-term rituximab maintenance up to five years in event-free survival (EFS) or overall survival (OS ). Here we report the final results with a median follow-up of 10 years.

Methods: 270 patients (median age 57 years: range 25-82) with untreated, relapsed, stable or chemotherapy resistant follicular lymphoma were treated with 4 doses of rituximab monotherapy in weekly intervals (375 mg/m²). Patients achieving at least a partial response were randomly assigned to receive maintenance therapy with one infusion of rituximab every 2 months, either on a short-term schedule (four administrations) or a long-term schedule (maximum of five years or until disease progression or unacceptable toxicity). The primary endpoint was EFS . Progression-free survival (PFS), OS, and toxicity were secondary endpoints. Comparisons between the two treatment arms were performed using the log-rank test for survival endpoints.

Results: 165 patients were randomly assigned to short-term (n=82) or long-term (n=83) maintenance. At a median follow-up period of 10 years, the median EFS is 3.4 years (95% CI 2.1-5.5) in the short-term arm and 5.3 years (95% CI 3.5-7.5) in the long-term arm. Using the pre-specified log-rank test this difference is statistically not significant (p=0.39 ). There is no significant difference in PFS and OS. Median OS in the short-term arm is 11.0 years (95% CI 11.0, NA ) and not reached in the long-term arm (p=0.80). The incidence of subsequent cancers increased in both arms over time, nine patients developed a subsequent cancer in the short-term maintenance arm and 10 in the long-term maintenance arm. There was no major additional toxicity with longer follow-up.

Conclusions : Even with a long follow-up of 10 years we were not able to show a significant benefit of long-term compared to short-term rituximab maintenance in EFS, PFS and OS. Treatment strategies and study designs need to take these results into consideration in order to guarantee optimal medical and scientific results.