Outcomes of patients with relapsed or refractory primary mediastinal B-cell lymphoma after frontline DA-EPOCH-R

Most patients diagnosed with primary mediastinal B-cell lymphoma (PMBCL) achieve cure following standard-of-care therapy with frontline DA-EPOCH-R (dose-adjusted etoposide, doxorubicin, cyclophosphamide, vincristine, prednisone, rituximab). However, treatment strategies following relapse after DA-EPOCH-R are not well defined. We, therefore, performed a retrospective review of PMBCL patients with relapsed/refractory (R/R) disease after frontline DA-EPOCH-R to obtain better insight into outcomes with salvage therapy and autologous stem cell transplant (SCT). Our cohort consisted of 107 patients with R/R PMBCL. Ninety patients qualified for the intention-to-treat salvage therapy analysis. With a median follow up of 48.9 months in the salvage therapy analysis, the median progression-free survival was 5.4 months (95% confidence interval [95% CI]: 2.3 months-not reached) with a 5-year overall survival rate of 78% (95% CI: 69-88). Compared to relapsed patients (relapsing >6 months after frontline DA-EPOCH-R, N=23), refractory patients (relapsing <6 months after frontline DA-EPOCH-R, N=67) had an inferior overall response rate (48% vs. 83%), complete remission rate (19% vs. 44%), and 2-year progression-free survival rate (30% vs. 69%) with initial salvage therapy. Forty-eight patients (53%) underwent autologous SCT after salvage therapy with estimated 5-year progression-free and overall survival rates of 85% (95% CI: 75-96) and 88% (95% CI: 79-99), respectively. There were no relapses among 29 patients in complete remission prior to autologous SCT. In conclusion, this analysis is the largest review of R/R PMBCL to date and demonstrates unfavorable outcomes for patients with refractory disease after frontline DA-EPOCH-R chemotherapy. Patients able to undergo autologous SCT, especially those in complete remission prior to the transplant, had excellent outcomes.