Prevalence of HPV Positivity and the Correlation Between P16INK4A Expression and HPV DNA Positivity in Carcinoma Oropharynx and Their Correlation With Survival Outcomes: A Retrospective Study From a Tertiary Cancer Centre in South India.

Introduction The incidence of oropharyngeal squamous cell carcinoma (OPSCC) has been increasing worldwide. High-risk human papillomavirus (HPV) infection is now a well-recognised risk factor for oropharyngeal cancers. However, the information regarding the prevalence and outcome of HPV-related OPSCC is sparse in India. The study was conducted to identify the frequency of HPV infection in oropharyngeal cancer and also to study the treatment response and survival according to HPV positivity and p16INK4A expression. Materials and methods The study sample consists of 100 paraffin-embedded tissue blocks of histologically proven OPSCC patients who had undergone treatment at a tertiary cancer centre in Kerala, India, from January 2010 to December 2012. The patients' medical records were examined to obtain demographic data, information on habits, and clinical, histopathological, and treatment information. Follow-up information on disease status and vital status was collected until May 2023. Paraffin-embedded tissue blocks of these patients were collected from the archives of the Division of Pathology. Immunohistochemistry (IHC) was used to identify p16 expression. HPV DNA was isolated from the paraffin-embedded tissue blocks by polymerase chain reaction. Statistical analysis and results Survival curves were obtained using the Kaplan-Meier method and compared with the log-rank test. The influence of p16 status and HPV DNA positivity on survival and recurrence was assessed using Cox regression. A total of 100 patients diagnosed with oropharyngeal malignancy and their paraffin-embedded blocks were used for the present study. p16 IHC was invalid for three patients, and 16 patients had invalid HPV DNA. Two patients were excluded from survival analysis because they had both invalid HPV DNA and p16 expression. A total of 98 patients were included in the analysis. Out of 98 samples assessed, 47 tested positive for p16 expression, 48 were negative, and three showed invalid results. Among the 98 patients, HPV DNA results were available for 82 patients. HPV DNA positivity was reported in 25 patients, and 57 samples were HPV negative. There was no significant correlation between p16 expression and HPV status. The median follow-up was 134 months (1-160 months). The five-year overall survival (OS) probability was 42.6% (95% confidence interval (CI) 28.49-56.71) and 51.2% (95% CI 35.92-66.48), respectively, for p16-negative and p16-positive tumours (p=0.689). The corresponding figures for five-year disease-free survival (DFS) were 49.0% (95% CI 34.7-63.3) and 51.9% (95% CI 36.62-67.18), p=0.959. The five-year OS for HPV DNA-negative tumours was 45.5% (95% CI 32-59.02) compared to 49.1% (95% CI 28.72-69.48) in HPV DNA-positive tumours. There was an absolute difference of 20% in five-year OS between double-positive and double-negative tumours. Conclusion This study demonstrated a p16 positivity rate of 49.47% and an HPV DNA positivity rate of 30.37%. However, only 15.18% of cases showed double positivity. No significant correlation was observed between p16 expression and HPV status. Double positivity (p16 and HPV positive) was associated with better OS and DFS compared to double-negative (p16 and HPV negative) and single-positive (either p16 positive or HPV positive) cases. This subgroup of patients might benefit from potential de-escalation strategies and should be the target population for future studies.