PD-L1 testing patterns in recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC) in the U.S.

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Pembrolizumab with/without platinum+5-FU is approved for the first-line (1L) treatment of R/M HNSCC, and its monotherapy use requires PD-L1 Combined Positive Score (CPS)≥1. We aimed to understand PD-L1 testing patterns and associations with patient characteristics and treatment choice in R/M HNSCC. Adults with R/M HNSCC initiating 1L systemic therapy were included from a U.S. nationwide database primarily compromised of community practices (07/01/2019-12/31/2023). PD-L1 testing patterns, treatment sequence, and time gaps related to testing and treatment initiation were summarized. Logistic regression was used to test associations between patient characteristics and PD-L1 testing patterns, and between CPS scores and 1L pembrolizumab monotherapy use. Of 2,207 patients, 32.7% received PD-L1 testing before 1L therapy initiation, 17.4% after 1L therapy initiation, and 50.0% were never tested. Most patients (55.9%) who tested positive before 1L therapy received pembrolizumab monotherapy while those who tested negative received pembrolizumab+platinum+5-FU most commonly (31.6%). Among patients untested before 1L therapy, the most common 1L treatment was pembrolizumab monotherapy (24.3%). Patients with an ECOG≥2 had higher odds of being tested before 1L therapy (OR: 1.42, p<0.01). CPS scores were associated with higher odds of receiving 1L pembrolizumab monotherapy (OR: 4.11 and 4.96 for CPS 1-19 and≥20, respectively; both p<0.0001). This study revealed low utilization of PD-L1 testing to guide treatment choice and impactful gaps between specimen collection, the receipt of results, and 1L therapy initiation. There is a need to improve clinician awareness of the importance of PD-L1 testing and an opportunity for updated guidelines on testing.