Use of pembrolizumab among older adults with cancer in the United States, before and after FDA approval of its tumor-agnostic indication.

INTRODUCTION: Pembrolizumab, an anticancer immunotherapy agent, has received multiple approvals since its first approval by the U.S. Food and Drug Administration (FDA) in 2014. Limited data exist on its real-world use and shifts post tumor-agnostic approval in 2017 for the treatment of patients with any microsatellite instability-high/mismatch repair deficient (MSI-H/dMMR) solid tumors. This study analyzes pembrolizumab's pre and post-tumor-agnostic approval use among older U.S. adults, revealing its evolving role in oncology practice.

METHODS: Using the Surveillance, Epidemiology and End Results (SEER)-Medicare data (2014-2019), we examined the cancer sites of pembrolizumab recipients before and after tumor-agnostic approval. Cancer sites were classified based on the timing of site-specific approvals (before/after tumor-agnostic approval) or no site-specific approval, and inclusion in MSI-H/dMMR clinical trials.

RESULTS: The total number of pembrolizumab recipients increased from 4221 in the pre-agnostic period to 20 479 in the post-agnostic period. Pembrolizumab was used for a broad range of cancer types, including cancers that had no FDA-approved site-specific indications at the time of use (25.8% in pre- and 24.6% in post-agnostic periods). The proportion of pembrolizumab recipients receiving pembrolizumab for cancers with site-specific approvals before tumor-agnostic approval decreased from 77.3% to 70.8%. The proportion of pembrolizumab recipients receiving pembrolizumab for cancers that gained site-specific approvals following tumor-agnostic approval almost doubled (6.8% to 13.0%). The proportion of pembrolizumab recipients with cancers included in MSI-H/dMMR trials also doubled (12.3% to 25.5%) following tumor-agnostic approval.

CONCLUSIONS: Pembrolizumab use has expanded over time among older adults with cancer, extending beyond those with FDA-approved site-specific indications.