Low-dose pembrolizumab for relapsed/refractory Hodgkin lymphoma: high efficacy with minimal toxicity.

Five patients with refractory/relapsed classical Hodgkin lymphoma (cHL), four having failed multiple lines of chemotherapy and brentuximab vedotin, were treated with low-dose pembrolizumab (median dose 100 mg, range: 100-200 mg, every 3 weeks). Complete response (CR) was achieved in four patients (80%), after a median cumulative dose of merely 495 (300-800) milligrams. Three CR patients have continued to receive pembrolizumab for a median of 16 (14-25) cycles, remaining in CR for a median of 18 (9-18) months. One CR patient underwent autologous hematopoietic stem cell transplantation and has remained in CR for 9 months. Partial response (PR) was achieved in one patient (20%), after a cumulative dose of 400 mg. The overall response rate was therefore 100% (CR: 80%; PR: 20%). Toxicity was virtually absent, with only grade 1 diarrhea and eczema each observed in one patient. Low-dose pembrolizumab was highly efficacious, achieving responses with minimal toxicity and at much lower costs.