Prognostic efficacy of combining tumor volume with Epstein-Barr virus DNA in patients treated with intensity-modulated radiotherapy for nasopharyngeal carcinoma

•Combining tumor volume with EBV DNA improves the accuracy of prognosis of NPC.•Patients with high EBV DNA levels, even with small tumor volumes, were at high-risk.•Tumor volume affect the prognosis for patients with high EBV DNA levels.

ObjectivesTo evaluate the prognostic effect of combining tumor volume with pre-treatment plasma Epstein-Barr virus DNA (EBV DNA) in patients treated with intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC).Materials and methodsA total of 180 consecutive NPC patients enrolled in this observational, prospective study and underwent IMRT. Tumor volume was delineated with IMRT planning system and plasma EBV DNA level was quantified by polymerized chain-reaction assay. The effects of tumor volume and EBV DNA level, either alone or in combination, on 5-year overall survival (OS) were cross-compared.ResultsThe 5-year OS in patients with gross tumor volume of nasopharynx (GTVnx) ⩽ 20 cc and >20 cc was significantly different (P = 0.001). The 5-year OS in patients with EBV DNA <6800 copies/mL and ⩾6800 copies/mL was also significantly different (P < 0.001). Based on the combination of GTVnx with EBV DNA, the 5-year OS in different subgroups was: low-risk (100%), intermediate-risk (87.8%, 95% CI: 70.6-95.2%) and high-risk (61.3%, 95% CI: 47.9-72.2%). Patients with small tumor volume and high EBV DNA level had a worse prognosis than those with large tumor and low EBV DNA level. Patients with low EBV DNA levels, and either small or large tumor volumes, had favorable prognosis. According to small or large tumor volume, patients with high EBV DNA level were divided into intermediaterisk and high-risk subgroups.ConclusionCombining tumor volume with pre-treatment plasma EBV DNA level altered survival-risk definition for subgroups of NPC patients and this combination, more than individual factors alone, improved the accuracy of prognostic evaluation.