Two years rituximab maintenance vs. observation after first-line treatment with bendamustine plus rituximab (B-R) in patients with mantle cell lymphoma: First results of a prospective, randomized, multicenter phase II study (a subgroup study of the StiL NHL7-2008 MAINTAIN trial).

7503 Background: Rituximab maintenance is part of a standard treatment approach for follicular lymphoma. In mantle cell lymphoma (MCL), however, it is not yet common practice. In this study we compared the effect of rituximab maintenance vs observation after first-line treatment with B-R in patients with previously untreated MCL. Methods: Patients were required to have stage II (with bulky disease > 7 cm), III, or IV disease for registration in this study. Primary endpoint was progression free survival (PFS). Secondary endpoints included response rates, overall survival (OS), time to progression, event free survival, toxicity. Patients were treated with up to 6 cycles of B-R plus 2 additional rituximab cycles. 120 Patients who have responded to B-R were then randomized to either rituximab maintenance (375 mg/m2every 2 months for a total of 2 years) or observation only. Results: A total of 120 patients were evaluable for the analysis, 59 (49%) were randomized to maintenance with rituximab and 61 (51%) to observation, respectively. Patient characteristics were comparable for both groups. Median patient age was 70 years, median time of observation was 54.2 months at the time of this analysis (January 2016). No significant difference in PFS between both arms could be observed (p = 0.130, 47 events, HR 0.64, 95% CI 0.36 – 1.14). The median for R maintenance was not yet reached, whereas for the observation arm the median was 54.7 months (95% CI 40.1. – n. y. r.). The results for overall survival showed no difference (p = 0.271, 27 events, HR 1.53, 95% CI 0.73 – 3.32) with a median of 69.6 months for R maintenance versus a median not yet reached in the observation arm. Conclusions: After a median observation time of 4.5 years, the results are yet inconclusive. Up to date we were not able to demonstrate statistical evidence supporting the benefit of R maintenance after B-R in the treatment of patients with MCL. Longer follow-up is needed before final results can be presented. Clinical trial information: NCT00877214.