Value of early evaluation of treatment response using 18F-FDG PET/CT parameters and the Epstein-Barr virus DNA load for prediction of outcome in patients with primary nasopharyngeal carcinoma

PurposeTo determine the value of early evaluation of response to concurrent chemoradiotherapy (CCRT) using F-18-FDG PET-derived parameters and the Epstein-Barr virus (EBV) DNA titre in outcome prediction in patients with primary nasopharyngeal carcinoma (NPC).MethodsSixty patients with primary NPC were prospectively enrolled. All patients underwent F-18-FDG PET/CT before and during CCRT. The plasma EBV DNA titre was measured along with the PET/CT-derived parameters. Changes in EBV DNA titre and PET/CT-derived parameters during CCRT were analysed in relation to response to treatment, recurrence-free survival (RFS) and overall survival (OS).ResultsA total lesion glycolysis (TLG) reduction ratio of 0.6 and a detectable EBV DNA titre during CCRT were predictors of an unfavourable response to treatment, RFS and OS. In multivariate analysis, a TLG reduction ratio of 0.6 predicted incomplete remission (p=0.002) and decreased RFS (p=0.003). The proportion of patients with a TLG reduction ratio of >0.6 who achieved a complete response was more than twice that of patients with a TLG reduction ratio of 0.6. A detectable EBV DNA titre, a TLG reduction ratio of 0.6 and older age were independently associated with a poorer OS (p=0.037, 0.009 and 0.016, respectively). A scoring system was developed based on these independent predictors of OS. Patients with a score of 1 and 2/3 had poorer survival outcomes than those with a score of 0 (hazard ratio 4.756, p=0.074, and hazard ratio 18.973, p=0.001, respectively). This scoring system appeared to be superior to the traditional TNM staging system (p<0.001 versus p=0.175).ConclusionEarly evaluation of response to CCRT using F-18-FDG PET-derived parameters and the EBV DNA titre can predict outcome in patients with primary NPC. A combination of interim PET parameters and the EBV DNA titre enables better stratification of patients into subgroups with different survival rates.