Prognostic value of F-18-FDG PET-CT metabolic index for nasopharyngeal carcinoma

The purpose of this study was to evaluate the prognostic value of metabolic tumor volume (MTV) and metabolic index (MI) from fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (F-18-FDG PET/CT) in patients with nasopharyngeal carcinoma (NPC). From October 2002 to July 2004, 41 patients with NPC who underwent F-18-FDG PET-CT scan before and after radiotherapy were reviewed retrospectively. All patients received intensity-modulated radiotherapy using 6MV X-rays. We examined the association of MTV and the results of long-term follow-up of the patients. Patients having tumors with an MTV below 30 cm(3) had significantly better 5-year overall survival (OS) (84.6:46.7%, P = 0.006) and disease-free survival (DFS) (73.1:40.0%, P = 0.014) than patients with an MTV of 30 cm(3) or greater. And the patients with MI below 130 had significantly higher 5-year OS (88.0:43.8%, P = 0.002) and DFS (76.0:37.5%, P = 0.005) than other patients. In the Cox multivariate analysis, MI and metabolic response (MR) were predictive of DFS, and we did not find a significant relationship between standard uptake value (SUV) and OS or DFS. The present study shows that tumor volume parameters, especially the combination of MTV and SUV in the metabolic index, are valuable for predicting long-term survival. High MI may be useful for identifying patients requiring more aggressive treatment.