Comparative Efficacy of First-Line Regimens in Relapsed/Refractory Mantle Cell Lymphoma (MCL): A Proportional Meta-Analysis

Introduction:

Mantle cell lymphoma (MCL) is an incurable B-cell malignancy that disproportionately affects the elderly. After first-line therapy failure, relapsed/refractory MCL assumes a more aggressive and universally fatal course. Currently, several classes of chemo/biologic therapies are approved in the second line. However, these agents and their combinations have not been compared head-to-head. We conducted this proportional meta-analysis to evaluate their relative impact on selected clinical outcomes.

Methods:

A review of the medical literature was conducted using online databases. Inclusion criteria consisted of English language; diagnosis of relapsed/refractory MCL; trials that explored the efficacy of first-line approved antineoplastic agents and their combinations that comprised: BTK-inhibitors (Ibrutininb (IB), Acalabrutinib, Zanubrutinib), Bortezomib (Velcade, VEL), Venetoclax (VEN), Lenalidomide (LEN), and Bendamustine+Rituximab (B-R); and studies reporting types of responses and duration of response. Proportional meta-analysis was conducted using random-effects model. The respective 95% confidence intervals were calculated, and funnel plots were constructed.

Results:

Thirteen studies comprising a total of 1,264 participants were included. The pooled overall response rates, ORR (95%CI), of the regimens were: 74% (66,81) BTK-inhibitors, 39% (25,53) VEL, 34% (24,46) LEN, 85% (78,92) B-R, 75% (58,92) VEN-IB, and 88% (79,97) IB-R. The pooled complete responses, CR (95%CI), of the regimens were: 33% (20,47) BTK-inhibitors, 9% (5,13) VEL, 6% (4,9) LEN, 45% (36,54) B-R, 42% (22,63) VEN-IB, and 44% (30,58) IB-R. There were no significant differences in ORR and CR between BTK-inhibitors, B-R, VEN-IB, and IB-R. ORR of VEL and LEN also did not significantly differ. However, ORR and CR of the former group were significantly higher than those of the latter. The pooled partial responses, PR (95%CI), of the regimens were: 41% (32,50) BTK-inhibitors, 28% (20,38) VEL, 28% (15,43) LEN, 41% (35,47) B-R, 34% (15,53) VEN-IB, and 44% (30,58) IB-R. There were no significant differences between PR of the regimens. The weighted duration of responses in months, DOR (95%CI), of the regimens were: 20 BTK-inhibitors, 9 VEL, 16 LEN, and 20 B-R.

Conclusions:

This proportional meta-analysis is the first to compare the current regimens in first-line relapsed/refractory MCL. It indicates that BTK-inhibitors monotherapy, IB combinations with R or VEN, and B-R provide equivalent ORR and CR rates that are significantly better than VEL and LEN with notably longer duration of response. It also raises questions about whether there is an additional ORR and CR benefits when adding VEN or R to IB in this clinical setting.