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

Background: 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.

Methods: 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.

Results: 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).

Conclusions: 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.