Prediction of Pathologic Grade and Prognosis in Mucoepidermoid Carcinoma of the Lung Using 18F-FDG PET/CT

Objective: The maximum standardized uptake value ($SUV_{max}$) of pulmonary mucoepidermoid carcinoma (PMEC) in fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography ($^{18}F$-FDG PET/CT) was evaluated as a preoperative predictor of pathologic grade and survival rate. Materials and Methods: Twenty-three patients who underwent preoperative PET/CT and complete resection for PMEC were enrolled. The optimal cut-off $SUV_{max}$ for tumor grade was calculated as 6.5 by receiver operating characteristic curve. The patients were divided into a high SUV group (n = 7) and a low SUV group (n = 16). Clinicopathologic features were compared between the groups by ${\chi}^2$ test and overall survival was determined by Kaplan-Meier analysis. Results: The mean $SUV_{max}$ was $15.4{\pm}11.5$ in the high SUV group and $3.9{\pm}1.3$ in the low SUV group. All patients except one from the low SUV group had low grade tumors and all had no nodal metastasis. The sensitivity and specificity of $SUV_{max}$ from PET/CT for predicting tumor grade was 85.7% and 93.8%, respectively. During the follow-up period (mean, $48.6{\pm}38.7$ months), four patients from the high SUV group experienced cancer recurrence, and one died of cancer. In contrast, none of the low SUV group had recurrence or mortality. Five-year overall survival rate was significantly higher in the low SUV group (100% vs. 71.4%, p = 0.031). Conclusion: Pulmonary mucoepidermoid carcinoma patients with high $SUV_{max}$ in PET/CT had higher tumor grade, more frequent lymph node metastasis and worse long-term outcome. Therefore, PMEC patients with high uptake on PET/CT imaging might require aggressive mediastinal lymph node dissection and adjuvant therapies.