Differences in real-world pembrolizumab dosing patterns (every 3 weeks versus every 6 weeks) across a large cancer center network.

Abstract

2592 Background: Pembrolizumab (pembro) is an intravenous immune checkpoint inhibitor used for anti-cancer treatment, with equivalent monotherapy dosing options of 200 mg every 3 weeks (Q3W) or 400 mg every 6 weeks (Q6W). Pembro Q6W dosing was approved for use in April 2020 after the Q3W dose had already been established. As pembro dosing patterns in real-world practice are not well-described, we evaluated this in a large cancer center network consisting of a central site (CS) and 36 community network sites (NS). Methods: We retrospectively reviewed the charts of all patients who received pembro monotherapy for cancer treatment between 4/2020 – 4/2022 at UPMC Hillman Cancer Center sites across the state of Pennsylvania, as well as sites in New York and Ohio. We performed statistical comparisons using the Fisher’s exact test and Wilcoxon rank-sum test. Results: We identified 1,640 patients who received pembro monotherapy, including 377 patients at the CS and 1,263 patients in the NS, with characteristics displayed. Pembro Q6W dosing was significantly more common at the CS than in the NS (42% vs. 15%, p<0.0001). When analyzed by tumor type, pembro Q6W dosing was significantly more common at the CS than in the NS for head & neck (53% vs. 11%, p<0.0001), thoracic (49% vs. 15%, p<0.0001), skin (60% vs. 19%, p<0.0001), and genitourinary (30% vs. 16%, p=0.015) cancers, but not for other tumor types. Within the NS, 30% (11/36) of sites only utilized pembro Q3W dosing and never administered Q6W dosing to patients. Of note, some patients who received pembro Q6W dosing received pembro Q3W dosing initially, either as part of a pembro-containing multidrug regimen or as monotherapy. Excluding patients initially treated with a multidrug regimen to reduce confounding factors, we found that of the patients who received pembro Q6W dosing, 47% (65/137) at the CS and 28% (48/169) in the NS were initially treated with pembro Q3W monotherapy before transitioning to Q6W monotherapy (p=0.0008). Conclusions: In our large cancer center network, pembro Q6W dosing was significantly more common at the CS than in the NS. Switching from pembro Q3W to Q6W dosing was also significantly more common at the CS. Further work is needed to clarify the patient, provider, and institutional factors influencing differences in pembro dosing patterns in real-world practice, as well as the impact of dosing patterns on care delivery outcomes such as cost and accessibility. [Table: see text]