Although we are hopeful that newer treatments such as anti-CD19 chimeric antigen receptor (CAR) T-cell therapy may be curative in a subset of patients with MCL, much longer follow-up data (eg, ≥5 years) are needed. As of right now, allo-SCT remains the only potentially curative approach in MCL.

Unfortunately, allo-SCT is only an option in a relatively small subset of patients with MCL. In fact, it has been reported that allo-SCT can be considered in just approximately 20% of all individuals who are diagnosed with MCL. A patient must be very fit and in good clinical remission to undergo allo-SCT, and this substantially limits the number of patients who can receive this treatment. Additionally, there is considerable transplant-related mortality associated with allo-SCT, even in a young and fit population. For instance, even with reduced-intensity therapy, nonrelapse mortality is roughly 10% to 24%, and there is also the potential for morbidity from acute and chronic graft-versus-host disease.

Nevertheless, there is a proportion of patients with MCL who are cured with allo-SCT, with reports of 5-year overall survival ranging from 40% to 60%. Therefore, this option must be considered for appropriate patients with relapsed/refractory MCL. It is also worth noting that allo-SCT continues to evolve, as does the management of graft-versus-host disease, so outcomes may improve in the future.

The question of whether CAR T-cell therapy might result in the cure of a similar number of patients is a tantalizing one, but we will need much longer follow-up. If you look at CAR T-cell data, the treatment-related mortality rate is typically under 5%, which is closer to the mortality that is expected from autologous SCT. It would be appealing to achieve the benefits of allo-SCT, including the potential for cure from CAR T cells, without the toxicities of allo-SCT. 

It is an exciting time in all of cancer, including in MCL with its tremendous heterogeneity. There is so much going on, and there are so many different opinions that it will be important to develop more consensus on the outlook. I think that clinical trials are very important, especially for rare diseases such as MCL, because retrospective studies ultimately cannot answer these questions.