Concurrent chemoradiotherapy is the established treatment for locally advanced nasopharyngeal carcinoma (NPC). However, there is no evidence supporting routine adjuvant chemotherapy. We aimed to demonstrate the effect of adjuvant chemotherapy on survival and distant metastasis in high-risk N3 NPC patients. We linked the Taiwan Cancer Registry and Cause of Death database to obtain data. Clinical N3 NPC patients were divided as those receiving definitive concurrent chemoradiotherapy (CCRT) with adjuvant 5-fluorouracil and platinum (PF) chemotherapy and those receiving no chemotherapy after CCRT. Patients receiving neoadjuvant chemotherapy were excluded. We compared overall survival, disease-free survival, local control, and distant metastasis in both groups using Cox proportional hazards regression analysis. Propensity-score matching was also performed to evaluate the independent effect of adjuvant PF in a matched cohort with similar baseline characteristics. We included 431 patients (152 and 279 patients in the adjuvant PF and observation groups, respectively). Median follow-up was 4.3 years. The 5-year overall survival were 69.1% and 57.4% in the adjuvant PF chemotherapy and observation groups, respectively (p = 0.02). Adjuvant PF chemotherapy was associated with a lower risk of death (hazard ratio [HR] 0.61, 95% confidence interval [CI] 0.43–0.84; p = 0.003), even after adjusting for baseline prognostic factors (HR 0.61, 95% CI 0.43–0.86; p = 0.005). Distant metastasis-free survival at 12 months was higher in the adjuvant PF chemotherapy group than in the observation group (98% vs 84.8%; p < 0.001). After adjusting for baseline prognostic factors, adjuvant PF chemotherapy was associated with freedom from distant metastasis (HR 0.11, 95% CI 0.02–0.46; p = 0.003). Adjuvant chemotherapy was also associated with a decreased risk of death (HR 0.59, 95% CI 0.41–0.85, p = 0.004) in a propensity score-matched cohort. Prospective evaluation of adjuvant PF chemotherapy in N3 NPC patients treated with definitive CCRT is warranted because adjuvant PF chemotherapy was associated with improved overall survival and decreased risk of distant metastasis.
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