Rituximab Maintenance Added to Ibrutinib-Containing Therapy in Younger, Untreated Patients With Mantle Cell Lymphoma: Results From the TRIANGLE Trial

: The TRIANGLE trial established an ibrutinib-containing therapy without autologous stem-cell transplantation (ASCT) as the new standard for younger, treatment-naïve patients with mantle cell lymphoma (MCL). However, the benefit of rituximab maintenance (RM) within this novel standard is unclear. We investigated whether RM improves progression-free survival (PFS) and overall survival (OS) with acceptable toxicity when added to the experimental arms of TRIANGLE. This secondary analysis of TRIANGLE included patients randomly assigned to ibrutinib-containing therapy without (I) or with (A + I) ASCT who responded to induction/ASCT. RM was given per national and center practice. PFS and OS of patients with and without RM were compared with inverse probability of treatment weighted Kaplan-Meier curves and log-rank tests. Among responders after induction/ASCT (I: 274; A + I: 237), RM was given to 61% (I) and 64% (A + I). RM prolonged PFS in ibrutinib-containing treatment arms (I: log-rank test: P = .003, 4-year PFS probability RM v no RM, 85% v 73%; A + I: P < .001, 90% v 75%). There were trends toward prolonged OS in RM groups. RM groups were at higher risk of grade 3 to 5 infectious toxicity (I: 34% v 11%; A + I: 41% v 18%). Our findings support adding RM to BTK inhibitor treatments in younger, untreated patients with MCL to achieve prolonged remission.