The results showed that 94%-98% of patients responded by the end of induction (defined as R-chemo and ASCT), with complete remissions in 36%-45% (from computerized tomography imaging, not PET scan). With a median follow-up of 31 months, failure-free survival (FFS; the primary study endpoint) was significantly improved for A+I vs A (3 year FFS of 88% vs 72%, respectively; p = 0.0008). In a subgroup analysis, FFS was notably improved for A+I in patients with high-level TP53 overexpression by immunohistochemistry. Toxicity did not differ during the induction and ASCT periods among the 3 arms regarding cytopenia, gastrointestinal disorders, and infections. However, neutropenia and infections were increased in the ibrutinib-containing arms during maintenance therapy—especially for Arm A+I.
The authors concluded that ASCT plus ibrutinib (Arm A+I) is superior to ASCT only (Arm A), and that Arm A is not superior to ibrutinib without ASCT (Arm I). No decision can yet be made regarding A+I versus I for which FFS to date remains very similar; however, the authors favor ibrutinib without ASCT due to lower toxicity. OS is trending to favor the ibrutinib arms, but longer follow-up will be needed to fully assess.
Should ASCT consolidation now be replaced by ibrutinib-containing induction R-CHOP/R-DHAP and maintenance ibrutinib, with or without maintenance rituximab? A definitive answer will require the fully-published TRIANGLE results, as well as ongoing analysis with longer follow-up. However, it seems very likely that ASCT indeed will be replaced by the new approach. TP53-mutated MCL should be treated with ibrutinib plus R-CHOP/R-DHAP and ibrutinib maintenance as validated in this trial.
Many centers have begun using a second-generation BTKi, acalabrutinib or zanubrutinib, rather than ibrutinib due to equivalent response rates with more favorable side effect profiles and fewer treatment discontinuations. Caution is warranted regarding simply adding a BTKi to one’s favored MCL induction regimen and foregoing ASCT—pending additional studies and the safety of such alternative approaches.
These are indeed exciting times of therapeutic progress, as they have been improving outcomes and providing longer survival outcomes for MCL patients. Targeted agents facilitate this shift to less intensive and chemotherapy-free regimens that provide enhanced response and mitigate short- and longer-term toxicities. More results will be forthcoming for MRD as a treatment endpoint, guiding maintenance therapy, and for risk-adapted treatment of newly-diagnosed and relapsing patients (based upon MCL subtype and biomarker profiles). Enrolling patients into clinical trials is strongly encouraged as the best mechanism to help answer emerging questions in the field and open the pathway to continued progress.