Among patients with heavily pretreated, relapsed or refractory primary mediastinal large B-cell lymphoma (PMBCL), pembrolizumab appears to induce long-term responses, with a subset of patients seeing a complete response (CR) for at least 4 years, according to research published in Blood.

A previous phase 1b study ( Identifier: NCT01953692) suggested that pembrolizumab may induce a response in this patient population, particularly among pretreated patients; this was followed by the phase 2 KEYNOTE-170 study ( Identifier: NCT02576990).

Although the findings from the initial analysis of KEYNOTE-170 were promising, long-term data were previously unavailable. In the present paper, researchers provided a long-term analysis from KEYNOTE-170.

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Overall, 53 patients with relapsed or refractory PMBCL were enrolled. The median follow-up was 48.7 months, and the median number of prior therapy lines was 3 (range, 2-8).

In this cohort, 13 (24.5%) patients completed 2 years of pembrolizumab monotherapy, while 40 (75.5%) discontinued treatment because of progressive disease (34%), clinical progression (22.6%), adverse events (11.3%), or physician decision (5.7%).

The investigator-assessed overall response rate was 41.5% (90% CI, 30-53.7), and 20.8% of patients had a CR. Among responders, 18 had an initial partial response, and 7 of these patients had a CR thereafter. The median duration of response was not reached.

No patients with a CR had disease progression by data cutoff, and none continued to subsequent therapy or transplantation.

The 4-year progression-free survival rate was 33% and the 4-year overall survival rate was 45.3%. Grade 3 or 4 adverse events were noted in 22.6% of patients, which included neutropenia (13.2%) and asthenia (1.9%). No grade 5 events were observed.

“The results of KEYNOTE-170 confirmed that PD-1 blockade is an effective and safe treatment option for [relapsed/refractory] PMBL, and an ongoing study (NCT04759586) is currently testing its role as first-line therapy,” the authors wrote in their report.

Disclosures: This research was supported by Merck. Please see the original reference for a full list of disclosures.


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

This article originally appeared on Hematology Advisor