Postradiation Metabolic Tumor Volume Predicts Outcome in Head-and-Neck Cancer

To explore the prognostic value of metabolic tumor volume measured on postradiation (18)F-fluorodeoxyglucose positron emission tomography (PET) imaging in patients with head-and-neck cancer.Forty-seven patients with head-and-neck cancer who received pretreatment and posttreatment PET/computed tomography (CT) imaging along with definitive chemoradiotherapy were included in this study. The PET/CT parameters evaluated include the maximum standardized uptake value, metabolic tumor volume (MTV(2.0)-MTV(4.0); where MTV(2.0) refers to the volume above a standardized uptake value threshold of 2.0), and integrated tumor volume. Kaplan-Meier and Cox regression models were used to test for association between PET endpoints and disease-free survival and overall survival.Multiple postradiation PET endpoints correlated significantly with outcome; however, the most robust predictor of disease progression and death was MTV(2.0). An increase in MTV(2.0) of 21 cm(3) (difference between 75th and 25th percentiles) was associated with an increased risk of disease progression (hazard ratio [HR] = 2.5, p = 0.0001) and death (HR = 2.0, p = 0.003). In patients with nonnasopharyngeal carcinoma histology (n = 34), MTV(2.0) <18 cm(3) and MTV(2.0) ≥18 cm(3) yielded 2-year disease-free survival rates of 100% and 63%, respectively (p = 0.006) and 2-year overall survival rates of 100% and 81%, respectively (p = 0.009). There was no correlation between MTV(2.0) and disease-free survival or overall survival with nasopharyngeal carcinoma histology (n = 13). On multivariate analysis, only postradiation MTV(2.0) was predictive of disease-free survival (HR = 2.47, p = 0.0001) and overall survival (HR = 1.98, p = 0.003).Postradiation metabolic tumor volume is an adverse prognostic factor in head-and-neck cancer. Biomarkers such as MTV are important for risk stratification and will be valuable in the future with risk-adapted therapies.