Radiotherapy dose and survival outcomes in human papillomavirus positive oropharyngeal cancer

Objective To evaluate the effect of definitive radiotherapy dose on survival in patients with human papillomavirus positive oropharyngeal carcinoma.Methods Human papillomavirus positive oropharyngeal carcinoma patients staged T1-3 and N0-2c, who received definitive radiotherapy (fraction sizes of 180 cGy to less than 220 cGy), were identified from the National Cancer Database 2010-2014 and stratified by radiation dose (50 Gy to less than 66 Gy, or 66 Gy or more).Results A total of 2173 patients were included, of whom 124 (6 per cent) received a radiation dose of 50 Gy to less than 66 Gy. With a median follow up of 33.8 months, patients had a 3-year overall survival rate of 88.6 per cent (95 per cent confidence interval = 87.1-90.1 per cent). On multivariate Cox analysis, a radiotherapy dose of 50 Gy to less than 66 Gy (hazard ratio = 0.95, 95 per cent confidence interval = 0.52-1.74, p = 0.86) was not a predictor of increased mortality risk.Conclusion Human papillomavirus positive oropharyngeal carcinoma patients had excellent outcomes with definitive radiotherapy doses of 50 Gy to less than 66 Gy. These results further support patients enrolling into clinical trials for radiation dose de-escalation.