Final KEYNOTE-170 Analysis Shows ‘Durable Responses’ to Pembrolizumab in PMBCL

By Cecilia Brown - July 17, 2023

Pembrolizumab showed “promising trends for long-term survival and acceptable safety” in patients with relapsed or refractory primary mediastinal B-cell lymphoma (PMBCL), according to the final analysis of the phase II KEYNOTE-170 trial.

Pier Luigi Zinzani, MD, PhD, of the Istituto di Ricovero e Cura a Carattere Scientifico Azienda Ospedaliero-Universitaria di Bologna Istituto di Ematologia and the Università di Bologna in Italy, and colleagues conducted the four-year follow-up analysis and published the findings in Blood.

The phase II study previously “demonstrated effective antitumor activity and acceptable safety of pembrolizumab” in patients with relapsed or refractory PMBCL, according to Dr. Zinzani and colleagues. The patients included in the study, who had disease progression following autologous hematopoietic stem cell transplantation (AHSCT) or were ineligible for AHSCT, received pembrolizumab 200 mg given every three weeks for up to 35 cycles.

The endpoints of the study included the objective response rate (ORR), progression-free survival (PFS), and duration of response (DOR) according to the investigator per 2007 Response Criteria; overall survival (OS); and safety.

With a median follow-up of 48.7 months, the ORR was 41.5%, including 20.8% of patients who had a completer response (CR) and 20.8% with a partial response. The median DOR was not reached and none of the patients who had a CR progressed at the data cutoff, according to the study’s investigators. The median PFS was 4.3 months, and the median OS was 22.3 months. The four-year PFS rate was 33% and the four-year OS rate was 45.3%.

At the data cutoff, more than half (56.6%) of patients had a treatment-related adverse event (AE) of any grade. Neutropenia, asthenia, and hypothyroidism were the most common AEs. Nearly one-quarter (22.6%) of patients had a treatment-related AE of grade 3 or 4. No grade 5 AEs were reported.

“After four years of follow-up, pembrolizumab continued to provide durable responses, with promising trends for long-term survival and acceptable safety in [relapsed or refractory] PMBCL,” Dr. Zinzani and colleagues concluded.


Zinzani PL, Thieblemont C, Melnichenko V, et al. Pembrolizumab in relapsed or refractory primary mediastinal large B-cell lymphoma: final analysis of KEYNOTE-170. Blood. 2023;142(2):141-145. doi:10.1182/blood.2022019340

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