Abstract 5241: Differences in PD-L1 expression by smoking status in HPV positive oropharyngeal cancer
Authors: Ramirez Ricardo J. , Wahle Benjamin , Liu Zixing , Mazul Angela , Zolkind Paul , Mansour Mena , Hyrc Krzysztof , Zevallos Jose P. 
Published: September 2020

Introduction: As the incidence of human papillomavirus-positive (HPV +) oropharyngeal squamous cell carcinoma (OPSCC) continues to increase, it is important to optimize treatment regimens. There is growing evidence demonstrating the efficacy and safety of anti-PD-1 immunotherapy, either as monotherapy or in combination with chemotherapy, for patients with programmed death-ligand 1 (PD-L1) positive head and neck squamous cell carcinoma. Greater PD-L1 expression has been associated with greater treatment response and improved overall survival independent of treatment modality. Prior studies have observed increased PD-L1 expression and improved treatment response in HPV(+) as compared to HPV(-) tumors. In contrast, HPV(-) disease, in which smoking is causative in most cases, is typically associated with unfavorable outcomes and lower rates of PD-L1 expression. In the present study, we sought to explore the effects of smoking on PD-L1 expression in HPV(+) tumors based on smoking status. We hypothesized that smokers would demonstrate lower levels of PD-L1 expression as compared to non-smokers.

Methods: Using an existing tissue bank, we identified a cohort of 52 HPV(+) tumors from patients with available smoking data. A tissue microarray was constructed with cores taken from the paraffin embedded tumor blocks. A single 0.5 micron slide was created and we examined PDL-1 expression by immunohistochemistry in 47 intact cores. Visiopharm software was used for quantitative analysis of area stained per total cellular area (Figure 2). Mann-Whitney U test was then performed to compare PD-L1 expression between current smokers and former/never smokers (Figure 1). Forty-four of the patients in the cohort had RNA-based Nanostring immuno-oncology assay data available. We were able to obtain paired quantitative IHC and Nanostring based PD-L1 (CD274) gene expression values for 40 patients and Spearman's correlation was performed (Figure 3).

Results: The primary tumor site was tonsil in 29 (56%) patients, 22 (42%) base of tongue, and 1 (2%) soft palate. Females made up 10% of the cohort. There were 9 (17%) current smokers, 20 (38%) former, and 23 (44%) never smokers. Pack-years was available for 22 (76%) of the current and former smokers (median: 30, range: 1-75 pack years). There were 5 patient deaths, and 10 patients experienced recurrence. PD-L1 expression on IHC was not predictive of death or recurrence (p=0.39 and p=0.07, respectively). Median follow up time was 20.5 months (range: 2.7 to 83 months). There was a significant difference in PD-L1 expression on IHC between current smokers and the former/never group (Figure 1). Relative gene expression of CD274 measured by the Nanostring assay was lower in current smokers as compared to former/never smokers, however this trend did not meet significance. There was a strong positive linear correlation between Nanostring based CD274 gene expression and PD-L1 expression on IHC (r=0.68, p &lt 0.0001).

Conclusion: Current smoking status at the time of diagnosis is associated with decreased PD-L1 expression as compared to former and never smokers. These results may have implications when considering immune checkpoint inhibition therapy in smokers with HPV(+) OPSCC.

Citation Format: Ricardo J. Ramirez, Benjamin Wahle, Zixing Liu, Angela Mazul, Paul Zolkind, Mena Mansour, Krzysztof Hyrc, Jose P. Zevallos. Differences in PD-L1 expression by smoking status in HPV positive oropharyngeal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5241.