Radiotherapy alone versus concurrent or adjuvant chemoradiotherapy for nasopharyngeal carcinoma patients with negative Epstein-Barr virus DNA post-induction chemotherapy.

6064 Background: Induction chemotherapy (IC) plus concurrent chemoradiotherapy has been recommended as the standard treatment for locoregionally advanced nasopharyngeal carcinoma(LA-NPC). However, concurrent chemotherapy was associated with increased toxicities, poor tolerance, and low completion rates. The aim of this study was to compare the efficacy and toxicity of IC+ radiotherapy (RT) and IC+ concurrent or adjuvant chemoradiotherapy (IC+CCRT/AC) in patients with negative post-IC EBV DNA. Methods: A total of 547 NPC patients with negative plasma EBV DNA post-IC were included. Patients were classified into the IC+RT group and the IC+ concurrent or adjuvant chemoradiotherapy (IC+CCRT/AC) group. Locoregional relapse-free survival (LRFS), distant metastasis-free survival (DMFS), overall survival (OS), and progression-free survival (PFS) were estimated and compared using the Kaplan-Meier method. Propensity-score matching (PSM) was performed to balance the variables. Results: The median follow-up time was 37 months. The 3-year LRFS, DMFS, OS, and PFS rates for the whole group were 92.2%, 92.4%, 96.4%, and 84.4%, respectively. There was no significant difference in LRFS, DMFS, OS, and PFS between the IC+RT and the IC+CCRT/AC group both before PSM (3-year rates of 91.1% vs. 92.6%, p = 0.94; 95.6% vs. 91.5%, p = 0.08; 95.2% vs. 96.8%, p = 0.80; 85.9% vs. 84.0%, p = 0.38) and after PSM (90.7% vs. 92.7%, p = 0.77; 96.8% vs. 93.7%, p = 0.29; 94.5% vs. 93.9%, p = 0.57; 84.7% vs. 85.6%, p = 0.96). Multivariate analysis demonstrated that treatment schedule was not an independent predictor for survival rates. Patients in the IC+RT group had fewer treatment-related acute toxicities and better tolerance. Conclusions: IC+RT displayed similar survival outcomes as IC+CCRT/AC for NPC patients with negative post-IC EBV DNA. Our current data seems not to support the routine use of concurrent or adjuvant chemotherapy after IC for unselected patients.