Impact of immunochemotherapy regimens on outcomes of patients with primary mediastinal B-cell lymphoma in the IELSG37 trial.

The IELSG37 trial enrolled 545 patients with primary mediastinal B-cell lymphoma (PMBCL) and demonstrated that consolidation radiotherapy (RT) can be omitted in patients with complete metabolic response (CMR), defined by the Lugano classification as Deauville score (DS) 1-3. This report evaluates outcomes following different frontline rituximab- and doxorubicin-based immunochemotherapy regimens chosen according to local practice. Patients treated with R-CHOP21 showed a significantly higher percentage of DS 5 than those on other regimens (23.8% vs. 8.2% average, P< 0.001) as well as a trend toward additional unplanned treatments (53.2% vs. 46.9%, P=0.30). The increased risk of poor response was confirmed in a multinomial logistic regression analysis adjusted for age, sex, IPI score, and performance status. R-CHOP21 was also associated with smaller reductions in MTV and less pronounced decreases in SUVmax. Patients with DS 5 more often received additional treatment (RT and/or salvage chemotherapy with or without autologous consolidation) after induction immunochemotherapy (96% vs. 41%, P< 0.001) and experienced significantly poorer outcomes. Although differences in progression-free and overall survival between R-CHOP21 and more aggressive regimens were not statistically significant, R-CHOP21 may increase the risk of additional treatments and may be inadvisable as frontline therapy for PMBCL. NCT01599559.