Diagnostic performance of ^18-F-FDG-PET–CT in adrenal lesions using histopathology as reference standard

Purpose: To determine the diagnostic performance of PET–CT in differentiating benign and malignant adrenal lesions when evaluating PET parameters individually as well as in combination with CT parameters, using histopathology as the reference standard. Methods: ¹⁸F-FDG-PET–CT scans of patients undertaken within 6 months prior to pathologic evaluation of their adrenal lesion(s) were evaluated. PET assessments consisted individually of maximum standardized uptake value of the adrenal lesion (A-SUV_max) and its (“normalized”) ratio to the liver (R-SUV_max). The diagnostic performances of these two PET parameters were also assessed when combined with the Hounsfield density from the non-contrast CT component of the PET–CT (A-HU). Diagnostic performance was assessed by area under the curve (AUC) of the receiver operating characteristics. Multiple logistic regression analysis was used to evaluate the individual and combined parameters. Results: The study cohort consisted of 61 adrenal lesions (59 patients). Malignant lesions (n = 52) had significantly higher median PET and CT parameters than benign lesions: A-SUV_max (11.4 vs. 6.1), R-SUV_max (3.3 vs. 1.7), and A-HU (37 vs. 24) [all p < 0.023]. AUC for the PET parameters individually was almost identical: 0.75 for A-SUV_max and 0.74 for R-SUV_max. On univariate analysis, thresholds of A-SUV_max >3.47 and R-SUV_max >0.83 yielded maximum accuracy (both 87%). The combination of these PET parameters individually with A-HU improved both AUC and accuracy (0.81% and 93%, respectively). Conclusions: The individual PET parameters A-SUV_max and R-SUV_max have similar diagnostic performance for differentiating malignant and benign adrenal lesions; their performance and accuracy improve when combined with the CT component (A-HU).