18F-FDG PET/CT in the evaluation of adrenal masses in lung cancer patients.

The aim of this study was to assess the usefulness of integrated (18)F-FDG PET/CT in differentiating benign from metastatic malignant adrenal masses in patients with lung cancer. One hundred and ten adrenal masses (size range, 0.5 - 6.3 cm, mean size, 1.9 cm) were evaluated retrospectively in 87 lung cancer patients. Integrated PET/CT images were assessed. PET findings were interpreted as positive if the (18)F-FDG uptake of the adrenal mass was greater than or equal to that of the liver. PET findings were interpreted as negative if the 18F-FDG uptake of the adrenal mass was less than that of the liver. All studies were reviewed independently by 3 nuclear medicine physicians, and the results were then correlated with clinical follow-up or biopsy results when available. PET/CT findings were positive in 77 adrenal masses. Seventy-four of these were eventually considered to be metastatic adrenal disease. In the remaining 3, in the course of follow-up, two underwent percutaneous puncture, and one underwent surgery. In the end, histopathological examinations of the adrenal lesions demonstrated the presence of adenomas. PET/CT findings were negative in 33 adrenal masses, of which 31 eventually proved to be benign. The 2 adrenal masses that were false-negative, underwent PET/CT twice with a two-month interval. At the initial study, the size was 0.5cm, 0.9cm in diameter, respectively. However, at the follow-up study, PET/CT showed both positive result with the size of 1.6cm, and 2.3cm in diameter, respectively. Both adrenal masses were interpreted as metastasis. The sensitivity, specificity, and accuracy for detecting metastatic disease were 97 %( 74 of 76), 94 %( 31 of 34), and 95% (105 of 110), respectively. The positive predictive value was 95 %( 74 of 77), and the negative predictive value was 94% (31 of 33). Integrated (18)F-FDG PET-CT is an accurate, noninvasive technique for differentiating benign from metastatic adrenal lesions detected on CT or MRI in patients with lung cancer. It allows early detection and accurate localization of adrenal lesions and differentiation of metastatic nodules from benign lesions, thereby facilitating treatment planning.