Metronomic chemotherapy in locoregionally advanced nasopharyngeal carcinoma with residual EBV-DNA after induction chemotherapy

To analyze outcomes and evaluate the survival benefits of metronomic chemotherapy (MC) with S-1 in locoregionally advanced nasopharyngeal carcinoma (LANPC) patients with residual EBV-DNA after induction chemotherapy (IC). We retrospectively included patients diagnosed with LANPC between October 2015 and August 2021. All patients were treated with IC and had residual EBV-DNA after IC. Chi-square test, Kaplan-Meier methods, and Cox proportional hazards model were used for statistical analyses. A total of 103 patients were identified, including 20 (19.4%) who received MC using S-1 for one year. Among these patients, 40 experienced disease progression, including 12 with locoregional recurrence (30.0%), 24 with distant metastasis (60.0%), and 4 with both locoregional recurrence and distant metastasis (10.0%). The 5-year locoregional recurrence-free survival, distant metastasis-free survival (DMFS), progression-free survival (PFS), and overall survival (OS) rates were 81.3%, 70.7%, 52.8%, and 72.1%, respectively. Multivariate prognostic analysis showed that post-IC residual EBV-DNA levels were independent prognostic factors for DMFS and PFS. Patients with EBV-DNA levels > 90 copies/mL had worse DMFS (hazard ratio [HR] 4.978, 95% confidence interval [CI] 1.413–17.535, P = 0.012) and PFS (HR 3.679, 95% CI 1.592–8.499, P = 0.002). Additionally, receiving MC was an independent prognostic factor for PFS and OS. Patients who received MC had better PFS (HR 0.310, 95% CI 0.120–0.802, P = 0.016) and OS (HR 0.100, 95% CI 0.013–0.745, P = 0.025). Our study highlights the poorer survival outcomes observed in LANPC patients with residual EBV-DNA levels following IC, as well as the potential survival advantages of MC in this subgroup. Not applicable.