Administration of oral maintenance chemotherapy for 1 year following definitive chemoradiotherapy may improve the survival of patients with stage N3 nasopharyngeal carcinoma

•Maintenance chemotherapy improve the survival of stage N3 nasopharyngeal carcinoma.•Toxicity of maintenance chemotherapy was slightly and tolerable.•The optimal duration of Oral maintenance S1 is recommended for ≥12 cycles. This study aims to evaluate the effectiveness and the optimal maintenance period of oral chemotherapy using S1 following definitive chemoradiotherapy in patients with stage N3 nasopharyngeal carcinoma (N3-NPC). A retrospective review was performed for N3-NPC treatment with maintenance chemotherapy (MC) [chemoradiotherapy (CRT)-MC] or without MC (CRT-non-MC) following definitive CRT between May 2014 and December 2017. Toxicities during MC were recorded. Overall survival (OS), progression-free survival (PFS), distant metastasis-free survival (DMFS) and locoregional relapse-free survival (LRRFS) were compared between CRT-MC and CRT-non-MC cohorts. The optimal duration of using maintenance S1 (MC-S1) was also analyzed. A total of 304 patients with stage N3-NPC were identified, of whom 56 were treated with CRT-MC and 248 with CRT-non-MC. After a median follow-up of 48 months, significant differences in OS (74.9 vs. 91.7%; P = 0.003), PFS (60.7 vs. 83.7%; P = 0.001) and DMFS (68.8 vs. 85.5%; P = 0.015) were observed between the CRT-non-MC and CRT-MC groups. Skin hyperpigmentation, leukopenia and fatigue were common but not severe (grade 1–2) side effects of MC. The OS, DMFS and PFS were significantly higher for patients who received S1 administration over a period of ≥12 cycles compared with those who received