Purpose: 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 ((18)F-FDG PET/CT) in patients with nasopharyngeal carcinoma (NPC).
Methods: From October 2002 to July 2004, 41 patients with NPC who underwent (18)F-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.
Results: 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.
Conclusions: 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.