Upper-Neck Versus Whole-Neck Irradiation at the Contralateral Uninvolved Neck in Patients With Unilateral N3 Nasopharyngeal Carcinoma

Abstract

Upper-neck irradiation (UNI) at the uninvolved neck has shown similar regional relapse-free survival as standard whole-neck irradiation (WNI) in patients with N0-1 nasopharyngeal carcinoma. However, whether UNI at the contralateral uninvolved neck is feasible in unilateral N3 disease, defined as >6 cm and/or below the caudal border of the cricoid cartilage, remains unclear. Data for 291 patients with nasopharyngeal carcinoma with unilateral N3 disease who were treated with intensity modulated radiation therapy from 2009 to 2015 were retrospectively analyzed. Among them, 190 received bilateral WNI (WNI group); the remaining 101 received WNI at the involved neck and UNI at the contralateral uninvolved neck (UNI group). Survival rates were estimated using the Kaplan-Meier method, and differences between groups were compared using the log rank tests. The median follow-up was 79.4 months (interquartile range, 56.0-89.3). Twenty-five patients had regional lymph node relapses (UNI: 10.9%, 11/101 vs WNI: 7.4%, 14/190; P=.31). Of these, 23 patients relapsed within the previously involved neck regions, while only 2 patients had relapses in the contralateral uninvolved neck (1 each in the UNI and WNI groups). Five-year regional relapse-free survival rates were similar between groups (89.7% vs 92.7%, P=.29). Similar between-group findings were also observed for 5-year overall survival (76.1% vs 80.4%, P=.40), distant metastasis-free survival (74.9% vs 79.2%, P=.44), and local relapse-free survival (95.6% vs 94.7%, P=.64). Furthermore, oncologic outcomes in subgroup and multivariable analyses were similar between groups. Regional control and survival outcomes were comparable in UNI at the contralateral uninvolved neck and standard WNI in patients with nasopharyngeal carcinoma with unilateral N3 disease. Our findings provide evidence for future radiation therapy guidelines of nasopharyngeal carcinoma.