Comparative analysis of the expression of р16, PD-L1 in squamous cell carcinoma of the oropharynx and CUP syndrome
Authors: Sokolova M. I. , Pavlova V. I. , Guz A. O. , Simonov A. V. 
Published: November 2024

Introduction. metastases in the absence of a primary tumor (cancer of unknown primary (Cup) syndrome) are diagnosed in 2–4 % of malignant tumor cases. This pathology is characterized by early metastatic dissemination, weak response to conventional chemotherapy, and aggressive progression. The use of checkpoint inhibitors targeting programmed cell death protein 1 (pD-1) and its ligand (pD-L1) has shown good results in treatment of various cancers including oropharyngeal squamous cell carcinoma (OpSCC). In Cup syndrome, the effectiveness of checkpoint inhibitors is rarely investigated, and pD-L1 expression is often not measured.Aim. To compare the frequency of p16 and pD-L1 hyperexpression in OpSCC and Cup syndrome, and to analyze dependency of survival rates on the level of expression of p16, the most important prognostic marker.Materials and methods. The study included 121 patients (59 with OpSCC and 62 with Cup syndrome) who received medical treatment in the multidisciplinary medical Center “medical City” (Tyumen) and Chelyabinsk Oncological Center of Oncology and Nuclear medicine between 2019 and 2023. Immunohistochemical examination was performed using the vENTANA Benchmark gX with primary antibodies against pD-L1 (clone Sp263, uSA) and р16 (uS Biological, uSA). Statistical analysis of the data was performed using SpSS 26 software. Long-term treatment outcomes were evaluated using 1-, 3-, 5-year survival rates and median survival. Overall survival was analyzed using the kaplan-meier method. Statistical significance of the differences was evaluated using the Cox model.Results. The studied groups did not differ by sex (p = 0.472), age (р = 0.640), and N stage (р = 0.262). patient age in the whole population varied between 42 and 81 years (median age 61.89 ± 11.9 years; mean age 60.81 ± 9.8 years). pD-L1 expression rate was higher in Cup syndrome at 92 % compared to 73 % in OpSCC (statistically significant difference; р = 0.01). Analysis of the association of ORSCC and Cup syndrome with human papilloma virus showed statistically significant difference in p16 hyperexpression: patients with OpSCC had p16-positive status more frequently (53 % of cases) while patients with Cup syndrome mostly had p16-negative status (73 % of cases). mean life expectancy of patients with OpSCC and p16-positive status was 62.65 months (95 % confidence interval 54.98–70.31), minimal observation period was 12 months, maximal was 70 months. mean life expectancy of patients with Cup syndrome and positive p16 status was 66.22 months (95 % confidence interval 56.35–76.10), minimal observation period was 12 months, maximal was 70 months. No statistically significant differences in survival rates of patients with OpSCC and Cup syndrome were found (р = 0.999).Conclusion. The study showed higher pD-L1 expression in patients with Cup syndrome compared to patients with OpSCC: 92 and 73 %, respectively (р = 0.01). The obtained results highlight the importance of routine pD-L1 expression evaluation in patients with Cup syndrome. The frequency of p16 hyperexpression was higher in OpSCC compared to Cup syndrome: 53 % versus 27 % (р = 0.02) which agrees with the worldwide epidemiological data: among all malignant neoplasms of the head and neck, Hpv infection is most common in OpSCC. Therefore, it serves as an important sign of hidden oropharyngeal cancer in Cup syndrome.