Pembrolizumab with R-CHOP in previously untreated diffuse large B-cell lymphoma: potential for biomarker driven therapy. Smith Stephen D,Till Brian G,Shadman Mazyar S,Lynch Ryan C,Cowan Andrew J,Wu Qian V,Voutsinas Jenna,Rasmussen Heather A,Blue Katherine,Ujjani Chaitra S,Shustov Andrei,Cassaday Ryan D,Fromm Jonathan R,Gopal Ajay K British journal of haematology Tumor programmed death-ligand 1 (PD-L1) expression in diffuse large B-cell lymphoma (DLBCL) is associated with inferior outcomes. The first-line immunologically-replete setting may be an opportune time for PD-1 inhibition. We evaluated pembrolizumab in combination with R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) in untreated patients with DLBCL. Eligible patients were age 18 or older, had adequate organ function, and had DLBCL requiring full-course therapy. Patients received pembrolizumab 200 mg/cycle with R-CHOP, primarily to assess toxicity. Response assessment utilized standard criteria, and PD-L1 staining was performed at a validated central laboratory. Among 30 patients, toxicity was comparable to standard R-CHOP but with two grade ≥3 immune related adverse events (rash, pneumonitis). The overall and complete response rate was 90% and 77%. With 25·5 months of median follow-up, 2-year progression-free survival (PFS) is 83%. PD-L1 expression was associated with non-GCB subtype, and improved PFS and survival. Pembrolizumab can safely be added to R-CHOP, and is associated with a high CR rate and 2-year PFS. Improved PFS with PR-CHOP in PD-L1 expressing tumors contradicts historical data in R-CHOP treated patients, supporting evaluation of PD-L1 as a biomarker to identify DLBCL patients who may benefit from this first-line strategy. 10.1111/bjh.16494