Long-term clinical outcome in nasopharyngeal carcinoma patients with post-radiation persistently detectable plasma EBV DNA

PURPOSE To investigate the long-term clinical outcome of nasopharyngeal carcinoma (NPC) patients with persistently detectable plasma EBV (pEBV) DNA after curative radiotherapy (RT). RESULTS The post-RT pEBV DNA levels were very lower copy number (median 21, interquartile range 8-206 copies/ml). After long-term follow-up, the relapse rate was 64.8%, the median time to progression 20 months, and 5-year overall survival (OS) 49.6%. Thirty-two of 39 (82.1%) patients with high viral load (≥ 100 copies/ ml) developed tumor relapse, whereas 57.0% (49/86) patients with low viral load (< 100 copies/ml) had tumor relapse (P = 0.0065). The 5-year OS rates were 20.5% and 62.9% for patients with viral load ≥ and < 100 copies/ml (median survival, 20 vs. 100 months; P < 0.0001). Patients who received adjuvant chemotherapy (AdjCT) experienced significant reduction in distant failures (66.2% vs. 31.6%; P = 0.0001) but similar locoregional recurrences (P = 0.2337). The 5-year OS rates were 69.4% for patients who received AdjCT compared with 33.2% for those of without AdjCT (median survival, 111 vs. 32 months; P < 0.0001). METHODS We screened 931 newly diagnosed NPC patients who finished curative RT and found 125 patients (13.4%) with detectable pEBV DNA one week after RT. The clinical characteristics, treatment modality, subsequent failure patterns and survivals were analyzed. CONCLUSIONS NPC patients with persistently detectable pEBV DNA after curative RT have a higher rate of treatment failure and poor survivals. Levels of the post-RT pEBV DNA and administration of AdjCT affect the final outcome significantly.