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.