Survival Benefit of Chemotherapy in Oropharyngeal Cancer Patients Treated with Surgery and Post-Operative Radiation

Abstract

Oropharyngeal squamous cell carcinoma (OPSCC) is the third most common cancer of the head and neck. The incidence of all subtypes of head and neck squamous cell carcinoma has decreased over the past 30 years in Canada and most of the world except for OPSCC. The increasing incidence of OPSCC over the past 10-20 years is driven by Human Papilloma Virus (HPV) type 16 infection. The benefit of chemotherapy in the post-surgical treatment of advanced stage OPSCC is unclear in the current literature especially after the emergence of HPV related OPSCC. This thesis investigated the survival benefit of adding chemotherapy in the primary surgical setting followed by adjuvant radiation therapy in the management of all patients with advanced stage OPSCC. We hypothesized that chemotherapy could have a survival advantage dependent on p16 and tobacco smoking history. Comparative survival analyses were performed between patients who received surgery + radiation therapy (S+RT) and surgery + chemoradiation therapy (S+CRT), stratified according to p16 status and tobacco smoking history. After adjustment for all covariates, smoking status and extracapsular extension were both independent predictors of survival. In our survival analysis for the whole cohort, the addition of chemotherapy was associated with a statistically significant better 5-year overall survival. After stratifying based on their p16 and smoking status, smokers showed a statistically significant better survival benefit from the addition of chemotherapy in post-operative setting. However, further prospective trials that include p16 and smoking status would be recommended to verify this hypothesis.