Primary Tumor Site as a Predictor of Treatment Outcome for Definitive Radiotherapy of Advanced-Stage Oral Cavity Cancers

Purpose To evaluate the outcome of definitive radiotherapy (RT) for oral cavity cancers and to assess prognostic factors. Methods and Materials Definitive RT was performed on 115 patients with oral cavity cancers at Stages III, IVA, and IVB, with a distribution of 6%, 47%, and 47%, respectively. The median dose of RT was 72Gy (range, 62–76Gy). Cisplatin-based chemotherapy was administered to 95% of the patients. Eleven patients underwent salvage surgery after RT failure. Results Eight-eight (76.5%) patients responded partially and 23 (20%) completely; of the patients who responded, 18% and 57%, respectively, experienced a durable effect of treatment. The 3-year overall survival, disease-specific survival, and progression-free survival were 22%, 27%, and 25%, respectively. The 3-year PFS rates based on the primary tumor sites were as follows: Group I (buccal, mouth floor, and gum) 51%, Group II (retromolar and hard palate) 18%, and Group III (tongue and lip) 6% ( p < 0.0001). The 3-year progression-free survival was 41% for N0 patients and 19% for patients with N+ disease ( p = 0.012). The T stage and RT technique did not affect survival. The patients who underwent salvage surgery demonstrated better 3-year overall survival and disease-specific survival (53% vs. 19%, p = 0.015 and 53% vs. 24%, p = 0.029, respectively). Subsite group, N+, and salvage surgery were the only significant prognostic factors for survival after multivariate analysis. Conclusion The primary tumor site and neck stage are prognostic predictors in advanced-stage oral cancer patients who received radical RT. The primary tumor extension and RT technique did not influence survival.