Metronomic S-1 Adjuvant Chemotherapy Improves Survival in Patients with Locoregionally Advanced Nasopharyngeal Carcinoma.

Purpose: This study aimed to investigate the efficacy and safety of using metronomic S-1 adjuvant chemotherapy in locoregionally advanced nasopharyngeal carcinoma (LANPC).

Materials and methods: We retrospectively collected data on patients diagnosed with LANPC between January 2016 and December 2021. All patients were treated with induction chemotherapy and concurrent chemoradiotherapy with or without metronomic chemotherapy (MC). Toxicities during MC were recorded. The chi-square test, Kaplan-Meier methods, propensity score matching (PSM), and Cox proportional hazards model were used for statistical analyses.

Results: A total of 474 patients were identified, including 64 (13.5%) and 410 (83.5%) patients with or without receiving MC, respectively. Patients who received metronomic S-1 had significantly better 3-year locoregional recurrence-free survival (LRFS) (100% vs. 90.9%, p=0.038), distant metastasis-free survival (DMFS) (98.5% vs. 84.1%, p=0.002), disease-free survival (DFS) (98.4% vs. 77.5%, p < 0.001), and overall survival (OS) (98.0% vs. 87.7%, p=0.008) compared to those without metronomic S-1. The multivariate prognostic analysis revealed that metronomic S-1 was identified as an independent prognostic factor associated with better DMFS (hazard ratio [HR], 0.074; p=0.010), DFS (HR, 0.103; p=0.002) and OS (HR, 0.127; p=0.042), but not in LRFS (p=0.071). Similar results were found using PSM. Common adverse events observed in the metronomic S-1 group included leukopenia, neutropenia, increased total bilirubin, anorexia, rash/desquamation, and hyperpigmentation. All patients with adverse events were grade 1-2.

Conclusion: It is worth conducting a randomized controlled trial to assess the effect of metronomic S-1 on survival outcomes and toxicities of LANPC.