Prognostic value of FDG PET metabolic tumor volume in human papillomavirus-positive stage III and IV oropharyngeal squamous cell carcinoma

OBJECTIVE. The purpose of this study was to establish the prognostic utility in human papillomavirus (HPV)-positive stage III and IV oropharyngeal squamous cell carcinoma (SCC) of the ¹⁸F-FDG parameters maximal, mean, and peak standardized uptake value (SUV_max, SUV_mean, and SUV_peak, respectively); metabolic tumor volume (MTV); and total lesion glycolysis (TLG). MATERIALS AND METHODS. We included 70 patients in the present study who had a biopsy-proven HPV-positive (by in situ hybridization) stage III and IV oropharyngeal SCC and had a baseline PET/CT examination at our institution. Outcome endpoint was event-free survival (EFS), which included recurrence-free and overall survival. Cox proportional hazards multivariate regression analyses were performed. Survival analysis was performed using Kaplan-Meier survival curves. RESULTS. In Cox regression proportional hazard univariate analysis, total MTV (hazard ratio [HR], 1.02; p = 0.008), primary-tumor MTV (HR, 1.02; p = 0.024), neck nodal MTV (HR, 1.03; p = 0.006), neck nodal TLG (HR, 1.01; p = 0.006), and neck node status (HR, 4.45; p = 0.03) showed a statistically significant association with EFS. There was no statistically significant association of EFS with SUV_max, SUV_mean, SUV_peak, and primary-tumor or overall TLG. In Cox regression proportional hazard multivariate model I, total MTV remained an independent prognostic marker for EFS when adjusted for every other variable individually in the model; in model II, primary-tumor MTV, neck node status, and SUV_peak are independent prognostic markers for EFS. The Kaplan-Meier survival curves using optimum cut point of 41 mL of total MTV were not significant (p = 0.09). CONCLUSION. Total MTV and primary-tumor MTV are associated with survival outcomes in patients with HPV-positive stage III and IV oropharyngeal SCC.