A Real‐Life Multicenter Study of Checkpoint Inhibitors in Relapsed/Refractory Primary Mediastinal B ‐Cell Lymphoma

The use of immune checkpoint inhibitors (ICIs) has deeply improved the outcome of relapsed or refractory (R/R) primary mediastinal B-cell lymphoma (PMBCL) patients. However, real-world data are still limited, and several aspects, including the need for consolidation strategies, remain to be fully elucidated. We report the results of the multicenter Italian retrospective observational PRIMICI study on R/R PMBCL patients treated with ICIs in a real-life (off-label) setting. Seventy-four patients, 42 treated with pembrolizumab and 32 with nivolumab-brentuximab vedotin (nivo-BV), were enrolled. The median follow-up was 34 months. The best overall response and complete response (CR) rates were 64% (n = 50) and 50% (n = 37), respectively. Of the 37 patients in CR, 11 received a consolidation treatment and 26 patients continued ICIs; CR were stable, independently from the use of consolidation, with a 4-year disease-free survival of 100%. The estimated 5-year progression-free survival (PFS) and overall survival (OS) were 60.4% (95% confidence interval [C.I.] 48.3%-70.6%) and 77.5% (95% C.I. 65.8%-85.6%), respectively. Nivo-BV was associated with faster and higher response rates and better OS compared to pembrolizumab. OS significantly improved after 2020 due to the use of salvage treatment with CAR T-cells. In conclusion, this study supported the safety and effectiveness of pembrolizumab or nivo-BV as a salvage therapy in R/R PMBCL patients. Importantly, the chance to obtain long-lasting responses, regardless of the use of a consolidation treatment, indicates that ICIs may be used with a curative intent in a significant subset of patients.