Long-term outcomes of consecutive patients of oropharyngeal cancer treated with radical radiotherapy.

Objectives: Given the wide variation in the incidence of Human Papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma (OPSCC), we aimed to evaluate the prevalence of HPV and assess treatment outcomes in patients with OPSCC treated with definitive radiotherapy (RT) with or without chemotherapy (CT) at a single institution in India.

Methods: Consecutive patients of OPSCC treated with definitive RT + /-CT in a tertiary care centre from January 2013 to December 2017 were analyzed. Kaplan-Meier method was used for survival analysis, and Log-rank test was used for univariate analysis.

Results: Six-hundred-thirty patients with OPSCC were treated with definitive RT + /-CT. The median age was 56 years (IQR 48-62). As per American Joint Committee on Cancer (AJCC) 7^th edition, 24 (3.8%) were stage I, 63 (10%) were stage II, 113 (18%) were stage III, 375 (59.5%) were stage IVA, and 55 (8.7%) were stage IVB. HPV status was known for 500 patients of which 55 (11%) were p16 immunohistochemistry positive. At a median follow-up of 73.3 months (IQR 58-89), 5-year local control (LC), loco-regional control (LRC), disease-free-survival (DFS) and overall survival (OS) were 48.1%, 35.6%, 29.2% and 34.5%, respectively. HPV-positive cohort showed significantly better outcomes compared to HPV-negative cohort with 5-year LC, LRC, DFS, OS of 84.4% vs 43.5% (p < 0.001), 71.3% vs 31.8% (p < 0.001), 63.9% vs 26.1% (p < 0.0001) and 69.1% vs 31.9% (p < 0.001) respectively.

Conclusion: The prevalence of HPV-positive OPSCC by p16 IHC was only 11% in our cohort. The outcomes of HPV-negative cancers are inferior when compared to HPV-positive cancers for a particular stage. Thereby justifying the need for development of treatment-intensifying strategies to improve the inferior outcomes.