Abstract
OBJECTIVES: Assessment of viable tumor residue after definitive radiotherapy is essential in patients with nasopharyngeal carcinoma (NPC). This study aimed to investigate the use of Hopkins criteria on positron emission tomography/computed tomography (PET/CT) for posttreatment response evaluation and whether plasma Epstein-Barr virus (EBV) DNA could bring additional value. MATERIALS AND METHODS: NPC patients who underwent FDG-PET/CT scan within 26 weeks after definitive radiotherapy were retrospectively reviewed. Residual disease was evaluated by Hopkins 5-point score. Accuracy of Hopkins criteria before and after incorporating EBV DNA was calculated. Prognostic value for locoregional failure-free survival (LRFFS) and disease-free survival (DFS) was analyzed. RESULTS: One hundred and sixteen patients were evaluated. Median follow-up time was 28.3 months (range 3.3-92.0 months). Residual disease was found in 19 (16.4%) patients. Overall, Hopkins criteria had high specificity (86.6%; 95% CI, 78.2%-92.7%) and negative prognostic value (NPV) (94.4%; 95% CI, 88.7%-97.3%), while sensitivity and positive prognostic value (PPV) was 73.7% (95% CI, 48.8%-90.9%), 51.9% (95% CI, 37.8%-65.6%), respectively. Posttreatment plasma EBV DNA was not predictive of residual tumor (P = .272). PPV and accuracy were 50.0% (95% CI, 32.1%-67.9%) and 83.0% (95% CI, 73.8%-90.0%) after incorporating detectable EBV DNA into the scoring system. Positive PET/CT results were significantly correlated with inferior 3-year LRFFS (95.7% vs 79.5%, P = .043) and 3-year DFS (84.6% vs 54.4%, P = .028). CONCLUSIONS: The Hopkins criteria demonstrated high NPV and specificity in posttreatment assessment, with the potential to be a reliable prognostic indicator for locoregional failure. Combining EBV DNA with PET/CT did not improve diagnostic accuracies. PET/CT should not be performed less than 12 weeks after treatment.