Objective: To evaluate whether pretreatment metabolic parameters obtained from positron emission tomography (PET) with [18F]fluorodeoxyglucose (FDG) can improve risk prediction for patients with oropharyngeal squamous cell carcinoma (OPSCC) treated with definitive intensity-modulated radiation therapy (IMRT).
Methods: Between 2003 and 2009, 86 patients with OPSCC had FDG-PET/CT prior to treatment with definitive IMRT. Chemotherapy was administered to 90 % of the patients. Metabolic tumor volume (MTV), total lesion glycolysis (TLG), maximum standardized uptake value (SUVmax), mean SUV (SUVmean), and inverse coefficient of variation (1/CoV) were analyzed for the primary tumor alone and the total of the primary tumor and involved lymph nodes.
Results: Median follow-up time for surviving patients was 41 months. On univariate analysis, total MTV and total TLG were significant predictors of disease-free survival (DFS) and overall survival (OS). SUVmax, SUVmean, and 1/CoV failed to predict DFS or OS. On multivariate analysis controlling for T- and N-classification, total MTV remained a significant predictor of DFS and OS. The optimal cutpoint for total MTV was 20.5 ml. A total MTV >20.5 ml was associated with a 4.13-fold increased risk of death (95 % confidence interval [CI], 2.12-8.05; p < 0.0001). Total MTV remained a significant predictor of DFS and OS for the subgroups with p16-positive (n = 25) and p16-negative (n = 18) cancer.
Conclusion: Total MTV is an independent predictor of DFS and OS for patients with OPSCC treated with definitive radiotherapy. Total MTV remained predictive of DFS and OS for both p16-positive and p16-negative cancer.
Keywords: HPV; Metabolic tumor volume; Oropharygeal cancer; Positron emission tomography; p16.