Benefit of chemotherapy in stage III nasopharyngeal carcinoma: Analysis of the surveillance, epidemiology, and end results database

•Overall, 1452 patients with stage III NPC with or without chemotherapy were analyzed.•A significant interaction existed between lymph node status and treatment modality.•Patients with node-positive stage III NPC benefited from chemotherapy.•No chemotherapy benefit for the node-negative stage III NPC was observed. Chemoradiotherapy is the standard treatment for locoregionally advanced nasopharyngeal carcinoma (NPC). We aimed to reveal factors associated with chemotherapy use and evaluate chemotherapy’s benefit in patients with stage III NPC stratified by lymph node status. Overall, 1452 patients with stage III NPC who underwent radiotherapy with (n = 1361) or without (n = 91) chemotherapy were identified in the SEER database. We examined predictors for chemotherapy use using logistic regression analysis. We compared all-cause mortality (ACM) and cancer-specific mortality (CSM) using the Kaplan-Meier method. Cox regression and competing risk analyses were used to evaluate the benefit of chemotherapy. The inverse probability of treatment weighting (IPTW) approach was applied to reduce selection bias and adjust for competing risks. Subgroup analyses and interaction effects were explored. Factors including age, sex, insured status, tumor grade, and N category were associated with chemotherapy use. Chemotherapy was associated with decreased 5-year ACM (31.4% vs. 48.4%, p