Effects of Epstein-Barr virus viral load and different treatment modality for stage III nasopharyngeal carcinoma.

Background: We investigated treatment results, the effects of different treatment modality, and pretreatment Epstein-Barr virus (EBV) viral load for stage III nasopharyngeal carcinoma (NPC) patients.

Methods: The initial definitive treatment for 356 stage III NPC patients consisted of concurrent chemoradiotherapy (CCRT) or induction chemotherapy plus radiotherapy (IndCT-RT). The pretreatment EBV DNA level separated patients into a high (n = 106) or low (n = 250) viral load (≥ or < 1000 copies/mL) subgroup. Outcome measures include relapse rates and various survivals.

Results: The 5-year rates of overall survival (OS), progression-free survival (PFS), distant metastasis failure-free survival (DMFFS), and locoregional failure-free survival (LRFFS) were 88.6%, 83.0%, 90.5%, and 90.5%, respectively. Patient characteristics and pretreatment viral load between IndCT-RT and CCRT were no significant differences except for a higher percentage of N2 disease in the IndCT-RT subgroup. Both treatment modality resulted in similar relapse rates (P = .56), OS (P = .20), PFS (P = .53), DMFFS (P = .89), and LRFFS (P = .35). However, patients with a high viral load experienced a higher relapse rate (33.0% vs 12.4%, P < .001) and worse OS (5-year rate, 79.0% vs 92.8%, P < .001), PFS (73.7% vs 88.4%, P < .001), DMFFS (80.2% vs 95.0%, P < .001), and LRFFS (85.6% vs 92.6%, P = .005) than those with a low viral load.

Conclusion: Long-term treatment results for stage III NPC patients are rather good. IndCT-RT can achieve the same treatment outcome as CCRT. Risk grouping by pretreatment viral load identified a subgroup (30%) of patients associated with a significantly higher relapse rates and worse survivals. These high-risk patients need to strengthen treatment intensity in future trials.