What is the significance of the recent TRIANGLE study on mantle cell lymphoma (MCL)?
Dr. LaCasce: The TRIANGLE study is extremely important in previously untreated, transplant-eligible patients with MCL. The cutoff age for transplants varies by center and is between 60 and 75 years. In the absence of a TP53 mutation, we have typically used induction chemotherapy followed by autologous stem-cell transplant (ASCT), followed by 3 years of maintenance rituximab. Obviously, this is a lot of therapy.
The TRIANGLE study was a 3-arm study in which ibrutinib-containing therapy was compared with standard RCHOP/RDHAP followed by ASCT. Maintenance rituximab became standard of care midway through the trial and was added. In the first experimental arm, ibrutinib was combined with RCHOP and then given as maintenance for 2 years following ASCT. The second experimental arm included the same schedule of ibrutinib and omitted the ASCT.
The results are early, but what has been presented thus far, ibrutinib induction and maintenance with ASCT is clearly superior to the standard arm with ASCT. Although the data are not statistically mature, the failure-free survival of the 2 ibrutinib arms was similar, suggesting that transplant may not be necessary. Longer follow-up is necessary to confirm this conclusion and assess overall survival in all 3 arms.
If the results hold, ASCT could become a thing of the past or perhaps used in the second line. With the favorable activity of chimeric antigen receptor (CAR) T-cell therapy, however, it is unclear whether ASCT would be used in second line. Avoiding the sequential use of ASCT and CAR T-cell therapy is appealing given the stem-cell damage that can result. It is appealing to think about not using ASCT upfront, because ASCT increases the risk of myelodysplastic syndrome.
The TRIANGLE data are likely to change the frontline management of MCL. Although ibrutinib was the first Bruton tyrosine kinase (BTK) inhibitor approved in MCL and has obviously changed the field dramatically, it is significantly less well-tolerated than the next generation of drugs—acalabrutinib and zanubrutinib. I suspect these will be substituted for ibrutinib and we will see even more tolerable upfront regimens for patients with newly diagnosed MCL.
Have there been any disparities that you found in patients newly diagnosed with MCL regarding age, sex, or ethnicity?
Dr. LaCasce: MCL typically affects patients in their 60s. It is rare in young patients, and approximately 75% of the cases are male. If you look at the demographics, it is more common in White patients and less common in Hispanic and African American patients. In addition, there is an association with farming, which likely contribute to the demographics of patients with MCL.
What is your recommended approach to managing patients newly diagnosed with MCL in your day-to-day practice?
Dr. LaCasce: Management is a bit tricky right now because the TRIANGLE study is not part of any guidelines thus far. Therefore, most would argue the standard treatment continues to include ASCT upfront. There is an important, large randomized study ( NCT03267433) going on in the United States that is assessing the role of ASCT in patients who are in MRD-negative complete remission at the end of induction therapy. These patients are randomized to ASCT plus maintenance rituximab versus maintenance rituximab alone.