(P31) Patterns of Failure Following Curative Treatment for Oral Cavity Squamous Cell Carcinoma, in Patients Receiving Post-Operative Radiotherapy +/- Chemotherapy, an Institutional Experience

Abstract

To analyze patterns of loco-regional failure and evaluate treatment outcomes of oral cavity cancer patients undergoing surgery and adjuvant radiotherapy +/- chemotherapy. Our institutional head and neck database was queried for patients with stage I-IVB oral cavity squamous cell carcinoma, treated primarily with surgery followed by radiotherapy +/- chemotherapy. These patients were treated between 1990-2016, with either 3D-conformal radiotherapy or intensity modulated radiotherapy (IMRT). We analyzed patient survival as well as local and regional patterns of failure. Out of 243 eligible patients, 229 had survival data recorded with median follow-up time of 50.1 months. The median survival for the entire cohort was 82.5 months, and median progression free survival was 9.3 months. The 2-year OS, LC, and LRC was 67.5%, 63.9% and 49.6%, respectively. The tumor subsites represented were oral tongue (36.2%), floor of mouth (23.9%), alveolus and hard palate (19.3%), buccal mucosa (5.8%), retromolar trigone (13.2%) and lip (1.6%). Of the patients with local control data available, 71 of 223 had experienced local or regional failure. The majority of failures (73.2%, 51 of 71) were in-field, followed by persistent disease (11 of 71), with 4 failures out-of-field and 4 with both in-field and out-of-field failures. Nearly three-quarters of local failures were in-field, and 15.5% of local failures consisted of persistent disease. The vast majority of local failures continues to be within the radiation treatment field for patients receiving post-operative radiotherapy.