Induction and Maintenance Therapy in Elderly Patients with Mantle Cell Lymphoma: Double-Randomized MCL R2 Elderly Clinical Trial By the European Mantle Cell Lymphoma Network

Background: Mantle cell lymphoma (MCL) formally remains an incurable disease. Recent trials in younger patients have demonstrated the benefit of a cytarabin-containing induction (Hermine, JCO 2022) and a rituximab (Le Gouill, NEJM 2017) as well as a lenalidomide maintenance (Ladetto, Lancet Haematol 2021). The MCL-R2 elderly trial investigated whether an induction with intermediate dose of cytarabine improves long term outcome over R-CHOP alone in elderly patients (>60 yrs). In addition, responders to induction therapy were randomized between a 2 year maintenance with rituximab-lenalidomide (R2) compared to rituximab alone. Here, we present the results of the 2 randomizations.

Methods: Patients >60 yrs not eligible for high dose therapy with stage II-IV MCL were included. Initially, patients were randomized between 8 cycles of 3-weekly R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone) or 6 cycles of alternating 3-weekly R-CHOP and 4-weekly R-HAD (rituximab, cytarabine, Dexamethasone). Subsequently, patients in complete or partial remission (CR, CRunconfirmed or PR) underwent a second randomization between rituximab maintenance every 2 months or R2 (lenalidomide 15 mg d2-22 every 4 weeks plus rituximab). Second randomization was stratified for induction regimen, study group, age, MCL international prognostic index (MIPI) and response (CR/CRu vs PR). Both maintenance regimens were continued for 24 months. The primary endpoint was EFS for the maintenance and overall survival for Induction therapy.

Results: Out of 624 patients from 7 countries, 620 were randomized for induction, 492 responded (78 % ORR, CR/CRu 41%) and 495 were randomized for maintenance. Median age was 71 yrs, 69% male, 85% stage IV, 47% intermediate and 46% high risk MIPI.

Response rate at the end of induction was similar in the 2 groups (OR 88% and 86% in the R-CHOP and R-CHOP/RHAD arm, respectively; CR 33% in both arms). No major safety difference were observed between the 2 induction arms. So far, PFS and OS were not different between the two induction regimen (70.6% vs. 66.8%; p=0.28 and 83% vs. 83% ; p=0.92 respectively: Figure 1A).

After a median follow-up of 4.2 years from maintenance randomization, patients in the R2 maintenance arm had a significantly improved PFS in comparison to R alone. The 4-year PFS was 60.9% in the R2 arm vs. 42.9 % in the R arm (p= 0.0002, figure 1B). Adverse events (AEs) were more pronounced in the R2 maintenance arm. Recurrent (> 5%) AEs grade >3 were: neutropenia (50.8% vs 19.2%), respiratory tract infection (6.3% vs. 0.8%), and skin cancer (5.9% vs 3.2%). In 46% of patients in the R2 arm, the dose of lenalidomide had to be reduced at least once. Overall survival (OS) was not different between the two maintenance arms, (R2: 87.6% and R: 85.1% at 2 years).

The majority of relapsed/refractory patients were treated with a BTK inhibitor alone or in combination (67.5%; 63% after R-CHOP and 71% after RHOP/RHAD).

Conclusions: While no efficacy or toxicity differences were observed between the two induction regimens (8x R-CHOP vs 6x R-CHOP/HAD), the combined R2 maintenance significantly prolonged PFS compared to rituximab alone. However, no difference in OS was observed, and toxicity was increased in the R2 arm.

Figure 1: OS(A) stratified by the CHOP and R-CHOP/RHAD arms and PFS (B) stratified by maintenance with rituximab (R) or rituximab-lenalidomide (R2) stratified by the four groups according to induction and maintenance arms.