Outcomes of intensity-modulated radiotherapy as primary treatment for oropharyngeal squamous cell carcinoma - a European singleinstitution analysis.

Abstract

To analyse survival and toxicity outcomes in patients treated with primary intensity-modulated radiotherapy (IMRT) for oropharyngeal squamous cell carcinoma (OPSCC) in the era of routine human papilloma virus (HPV) testing. Single-institution case series. Tertiary Head and Neck Cancer Unit. A total of 186 patients received IMRT (+/- chemotherapy) for radical primary treatment of OPSCC between March 2010 and December 2013. HPV status was available for 88% of cases. Median radiation dose was 65 Gy in 30 daily fractions. 90% of stage III/IV patients received concurrent chemotherapy or cetuximab. Overall, disease-free and disease-specific survival; rates of late xerostomia and dysphagia. A total of 177 patients completed treatment (Stage I/II: 23; Stage III/IV: 154), with median follow-up of 26 months. Estimated 3-year overall survival (OS), disease-free survival (DFS) and disease-specific survival (DSS) rates were 77.2% (70.5-83.9), 72.3% (65.4-79.2) and 80.2% (74.1-86.3). Estimated 3-year OS, DFS and DSS for HPV-positive patients were 90.9% (85.2-96.6), 87.9% (81.4-94.4) and 91.8% (86.3-97.3). A previously identified risk stratification method was validated, showing improved OS for low-risk over high-risk patients (HR 0.09, P < 0.001). The 2-year feeding tube retention rate was 6%, and 2-year grade ≥2 xerostomia rate was 38% (23% if mean contralateral parotid dose <24 Gy). Outcomes with IMRT are favourable, particularly in the HPV-positive patient group. This data further supports the use of a previously described prognostication model that can be used to select patients for escalation/de-escalation clinical trials.