Long-term survival analysis of nasopharyngeal carcinoma by plasma Epstein-Barr virus DNA levels.

Background: The objective of this study was to confirm the relation between plasma Epstein-Barr virus (EBV) DNA (pEBV DNA) load and treatment outcomes after long-term follow-up in patients with nasopharyngeal carcinoma (NPC).

Methods: In total, 210 patients with NPC were enrolled, including 99 previously reported patients and 111 new patients. They prospectively received treatment with induction chemotherapy plus radiotherapy and were followed for at least 6 years. In these patients, pEBV DNA levels were measured before treatment and 1 week after treatment. The plasma viral load was correlated with treatment outcomes in the group of new patients and in the entire group.

Results: By using previously defined pEBV DNA cutoff values (1500 copies/mL pretreatment and 0 copies/mL post-treatment), there was a significant correlation between the pEBV DNA value and relapse-free survival, overall survival, and subsequent relapse rates in the new, independent patient cohort. Outcome analyses for the entire group revealed a higher relapse rate (45.6% vs 21.5% [P = .0037] or 76.7% vs 26.1% [P < .0001]), a worse relapse-free survival rate (56.5% vs 79.3% [P < .0001] or 23.3% vs 75.6% [P < .0001]), and poorer overall survival (59.2% vs 86% [P = .0003] or 33.3% vs 79.4% [P < .0001]) in patients who had high pretreatment or persistently detectable post-treatment pEBV DNA levels, respectively, versus their respective counterparts. Multivariate Cox analysis also confirmed these results.

Conclusions: In this expanded study, the prognostic significance of pEBV DNA was confirmed using predefined cutoff values in an independent patient group, and pEBV DNA was identified as an independent prognostic marker for NPC.