Utility of metabolic heterogeneity factor in differentiating malignant versus benign parotid uptake on F-18 FDG PET-CT

Differentiation of benign and malignant parotid uptake on Fluorine 18 Fluro-Deoxy-Glucose Positron Emission Tomography-Computed Tomography (¹⁸F FDG PET-CT) is of paramount importance due to the poor prognosis of the later but usual quantitative measures such as standardized uptake value (SUV) are not reliable for this purpose. Metabolic heterogeneity, being a characteristic of malignant tumors, would potentially be able to make this distinction. In this study, seventy-one FDG-avid parotid lesions were retrospectively separated histologically into benign and malignant groups. The heterogeneity factor (HF) of all the lesions was then calculated and compared between the two groups. There was significant difference in HF between malignant (median -0.17) and benign group (median -0.03); P=0.0006. On receiver operating characteristic (ROC) analysis, a cut-off value of ≤ -0.06 for HF was associated with the highest sensitivity and specificity (sensitivity and specificity of 94.6% and 60.0%, respectively-AUC=0.789; P=0.0001). Hence, it was concluded that HF is a reliable value in distinguishing benign from malignant parotid uptake on ¹⁸F FDG PET-CT.