Individual and Cumulative Impacts of Diagnosis‐to‐Treatment Interval and Radiotherapy Interval on Survival in Nasopharyngeal Cancer

OBJECTIVE: To evaluate the impact of diagnosis-to-treatment interval (DTI) and radiotherapy interval (RTI) on overall survival (OS) in locally advanced nasopharyngeal carcinoma (LA-NPC) treated with concurrent chemoradiotherapy (CCRT). STUDY DESIGN: Retrospective database study. SETTINGS: Single tertiary academic center. METHODS: We analyzed 285 LA-NPC patients treated with CCRT between 2010 and 2024. Receiver operating characteristic (ROC) analysis was used to derive optimal thresholds for DTI and RTI. OS was estimated using the Kaplan-Meier method and compared with log-rank tests. Multivariable Cox models assessed independent associations, with hazard ratios (HRs) reported with 95% confidence intervals (CIs). RESULTS: After a median follow-up of 75.6 months, median OS was 108 months. ROC-derived thresholds of 30 days for DTI and 49 days for RTI were applied. DTI ≤ 30 days was associated with improved OS compared with >30 days (not reached vs 64.0 months; P < .001), as was RTI ≤ 49 versus >49 days (122.0 vs 74.0 months; P < .001). On multivariable analysis, DTI > 30 days (HR: 2.56, 95% CI: [2.11-3.82], P < .001) and RTI > 49 days (HR: 1.65, 95% CI: 1.09-2.47, P = .002) were independently associated with inferior OS. Patients with both delays had the poorest survival (median OS: 51.0 months). DTI > 30 days was associated with increased distant metastasis, whereas RTI > 49 days was associated with higher locoregional failure. CONCLUSION: DTI > 30 days and RTI > 49 days are independently associated with worse survival in LA-NPC treated with definitive CCRT. These findings support timely treatment initiation and uninterrupted radiotherapy delivery.