(637) PD-L1 expression in Oral Cavity Squamous Cell Carcinoma

Introduction: An increasing number of women, young patients, and those with low tobacco exposures are developing oral cavity squamous cell carcinoma (OCSCC)​ for unknown reasons. Immune-related factors may contribute to or correlate with OCSCC in the absence of traditional risk factors. We examined if tumor driven immune suppression, as quantified by combined positivity score (CPS), correlates with different patient presentations.

Methods: All patients who underwent surgical resection of OCSCC at a tertiary academic center with a reported CPS (2015-2025) were included. Demographics, tumor pathology, and treatment information were collected. Univariate analyses between CPS and clinicopathologic features were evaluated using Spearman rank correlation or Wilcoxon rank-sum tests. Multivariable linear regression was performed for CPS as a continuous, log-transformed outcome. Given prevalence of high CPS, an exploratory analysis dichotomizing CPS at ≥20 was performed using univariate tests and multivariable logistic regression.

Results: Of 120 patients, 116 (97%) had CPS ≥1, 101 (84%) had CPS ≥10, and 94 (78%) had CPS≥20. CPS was not correlated with age, or with pathologic T or N classification. CPS distributions did not differ by tobacco exposure or sex. Similarly, there were no differences in pathologic characteristics (depth of invasion, lymphovascular invasion, perineural invasion) between groups. On multivariable linear regression, no significant associations were found, and overall model fit was low. High CPS≥20 was also not associated with these variables. 15 (60%) patients with recurrent disease after initial definitive treatment received immunotherapy. Of 11 patients with response information, there was 1 complete response, 2 partial responses, and 8 with disease progression.

Conclusions: In this study, CPS appears independent of traditional risk factors and disease burden. Future larger prospective studies that also assess responses to immunotherapy are needed to explore immune-related differences between these distinct patient groups.