The effect of adding concurrent chemotherapy to radiotherapy for stage II nasopharyngeal carcinoma with undetectable pretreatment Epstein-Barr virus DNA: Retrospective analysis with a large institutional-based cohort.

Little is known about the value of adding concurrent chemotherapy (CC) to radiotherapy for stage II nasopharyngeal carcinoma (NPC) with undetectable (0 copies/mL) pretreatment Epstein-Barr Virus (EBV) DNA in the intensity-modulated radiotherapy (IMRT) era. To address this question, the present study retrospectively reviewed 514 patients with newly diagnosed stage II NPC and undetectable pretreatment EBV DNA from Sun Yat-sen University Cancer Center between March 2008 and October 2016. Clinical characteristics and survival outcomes between concurrent chemoradiotherapy (CCRT) and IMRT alone groups were compared. Propensity score matching analysis was conducted to control for confounding factors. Although CCRT group had significantly higher proportions of stage N1 disease than IMRT alone group before matching (85% vs. 61%, p < 0.001), no statistically significant differences were noted for OS (97.8% vs. 98.1%, p = 0.700), DFS (93.4% vs. 94.5%, p = 0.846), DMFS (96.0% vs. 96.9%, p = 0.762), and LRFS (97.3% vs. 98.1%, p = 0.701). After 1:1 propensity-score matching, 177 pairs were identified. Patients in each group were found to be well balanced in baseline characteristics and risk factors (all P > 0.05). The five-year OS (96.9% vs. 98.2%, p = 0.302), DFS (92.0% vs. 95.2%, p = 0.777), DMFS (95.2% vs. 97.6%, p = 0.896), and LRFS (97.3% vs. 97.6%, p = 0.328) rates remain comparable for both CCRT and RT alone groups. Additionally, subgroup analysis still failed to observe any significant survival benefit for the addition of CC to IMRT for N1 disease (P>0.05 for all). Our results indicated that IMRT alone appeared to achieve comparable survival to CCRT for stage II NPC with undetectable pretreatment EBV DNA.