Patterns and prognosis of regional recurrence in nasopharyngeal carcinoma after intensity‐modulated radiotherapy

OBJECTIVE: We analyzed the patterns of lymph node (LN) failure and prognosis in patients with regional recurrent nasopharyngeal carcinoma (rNPC) alone after primary intensity‐modulated radiotherapy (IMRT). METHODS: A total of 175 patients who were treated with IMRT between 2010 and 2015 and who experienced regional recurrence alone were included. Recurrent LNs were re‐located in the initial pretreatment imaging and IMRT plan and failures were classified as in‐field or out‐field based on target volume delineation. All patients underwent curative salvage treatment. Independent prognostic factors for overall survival (OS) were selected by multivariate Cox analysis. RESULTS: Level IIb (49.1%, 86/175) was the most frequent recurrence site, followed by level IIa (36%), level III (18.9%), level IVa (12%), the retropharyngeal region (8%), level Va (6.9%), and the parotid region (6.9%). A total of 264 recurrent LNs were recorded: 149 (56.4%) were classified as in‐field failure with a prescribed dose ≥66 Gy, 60 (22.7%) with 60 to <66 Gy, 32 (12.1%) with 50 to <60 Gy, and 23 (8.7%) as an out‐field failure, which mainly occurred in the parotid region and level Ib. After a median follow‐up of 52.8 months, the estimated 5‐year OS rate was 66.9%. Multivariate analysis showed that age, plasma Epstein–Barr virus DNA level, extranodal extension, lower neck involvement, and parotid LN recurrence were independent prognostic factors of OS. CONCLUSIONS: In‐field failure represented the main pattern of regional recurrence and out‐field failure mainly occurred in the parotid gland and level Ib. Patients with regional rNPC alone had a good prognosis after salvage treatment.