FDG-PET Measurement of Metabolic Tumor Volume Predicts Oropharyngeal Squamous Cell Carcinoma Survival
“Total MTV (metabolic tumor volume) ≥20.5 ml was associated with a 4.13-fold increased risk of death,” reported lead author Adam Garsa, MD, at the Siteman Cancer Center's Department of Radiation Oncology, Barnes-Jewish Hospital and Washington University School of Medicine in St. Louis, Missouri, and coauthors. “Total MTV is an independent predictor of DFS (disease-free survival) and OS (overall survival) for patients with OPSCC treated with definitive radiotherapy.”
The study included 86 patients with OPSCC who underwent FDG-PET functional tumor imaging prior to treatment with intensity-modulated radiotherapy (IMRT) between 2003 and 2009. Most (90%) of the patients also received chemotherapy.
FDG-PET/CT measurements of MTV (the volume of metabolically-active tumor tissue), total lesion glycolysis (TLG), and maximum standardized uptake values (SUVmean, the average FDG uptake by a tumor) were measured for primary tumors and involved lymph nodes. At a median follow-up time of 41 months, total MTV and TLG predicted DFS and OS. When T- and N-classification status were statistically controlled in subsequent multivariate analyses, total MTV – but not TLG – “remained a significant predictor of DFS and OS,” the authors reported.
Tumor expression of protein p16INK4a (p16) was also assessed in subgroup analysis.
A “total MTV ≥20.5 ml was associated with a 13.0-fold increased risk of death (95% CI, 1.62-100; P=0.016) for the p16-positive subgroup, compared to a 4.27-fold increased risk of death (95% CI, 1.28-14.3; P=0.018) for the p16-negative subgroup,” they reported.
“To our knowledge, this is the first report analyzing FDG-PET parameters in both p16-positive and p16-negative disease,” the authors noted. “Our results indicate that total MTV is a significant prognostic factor for oropharyngeal cancer, even after controlling for T- and N-classification. Thus, total MTV does not simply act as a surrogate for stage, but serves as an independent prognostic factor.”