Combination of smoking and Epstein-Barr virus DNA is a predictor of poor prognosis for nasopharyngeal carcinoma: a long-term follow-up retrospective study

Background This retrospective study was performed to determine the prognostic potential of smoking and its combination with pre-treatment plasma Epstein-Barr virus (EBV) DNA levels in patients with nasopharyngeal carcinoma (NPC). Methods Medical records of 1080 non-metastatic NPC patients who received intensity-modulated radiotherapy were reviewed. Male patients were categorized as never and ever smokers, and the smoking amount, duration, and cumulative consumption were used to evaluate dose-dependent effects. Survival outcomes were assessed using Kaplan-Meier survival analysis and the multivariate Cox regression analysis. Propensity score matching (PSM) was constructed. Results The 5-year overall survival (OS) was worse for ever smokers than never smokers, and significantly decreased with the increase of smoking amount, duration, and cumulative consumption. Compared with never smokers, the multivariate-adjusted hazard ratio (HR) of death was higher in ever smokers (HR = 1.361, P = 0.049), those smoked ≥20 cigarettes/day (HR = 1.473, P = 0.017), those smoked for ≥30 years (HR = 1.523, P = 0.023), and those cumulative smoked for ≥30 pack-years (HR = 1.649, P = 0.005). The poor prognostic effects of smoking was also confirmed in the PSM analysis. The combination of cumulative smoking consumption and pre-treatment EBV DNA levels was proven to be an independent poor prognostic factor for male NPC, and the risk of death, progression, and distant metastases gradually increased with both factors ( P < 0.001). Conclusions Combination of smoking and pre-treatment EBV DNA levels as a predictor of poor prognosis could further improve the risk stratification and prognostication for NPC.