Clinical Outcomes And Prognostic Factors After Intensity Modulated Radiotherapy For T3 Nasopharyngeal Carcinoma

Background:To evaluate the effectiveness and analyze the prognostic factors in T3 nasopharyngeal carcinoma (NPC) after intensity modulated radiotherapy (IMRT)Methods:A total of 348 non-metastatic NPC patients treated with IMRT (96.8%with chemotherapy) were retrospectively reviewed. All the primary tumors were defined as T3 stage according to the 7th UICC/AJCC staging system. The prognostic significance of different skull base parts, retropharyngeal lymph nodes (RLN), nodal laterality, necrosis, extracapsular spread (ECS), maximal diameter, levels involved and N staging system efficiency of the 7th UICC/AJCC and Chinese 2008 were analyzed.Results:With a median follow up of 51 months, the 4-year local relaps-free survival (LRFS), regional relaps-free survival (RRFS), distant metastasis-free survival (DMFS) and overall survival(OS) for T3 NPC patients were 93.7%,93.9%,83.5% and 90.9%. Petrous apex(no vs yes) and N stage(N0-1 vs N2-3) was the independent prognostic factors for OS. And N stage was also related with DMFS and DFS. Nodal laterality was independent prognostic factor for DMFS, OS and DFS in multivariate analyses within positive cervical lymph node patients. There is no statistically significant difference among RLN, nodal necrosis, ECS, maximal diameter, levels involved in patients with positive cervical lymph node. Thus we compared the efficacy of the 7th edition of UICC/AJCC N staging system and Chinese 2008 N staging system for T3 patients. The latter provided a better distinction from hazard ratio in DMFS and DFS than the former.Conclusions:IMRT provides excellent locoregional control for T3 patients with nasopharyngeal carcinoma. Distant metastasis remains as the major cause of treatment failure. More prognostic factors need to be explored further for strengthed treatment strategy. A more predictive N staging system is needed for T3 stage NPC.