18F-FDG PET in Evaluation of Adrenal Lesions in Patients with Lung Cancer

The purpose of this study was to assess the role of PET with 18F-FDG in differentiating benign from metastatic adrenal masses detected on CT or MRI scans of patients with lung cancer. Methods: This retrospective study analyzed 18F-FDG PET scans of patients with lung cancer who were found to have an adrenal mass on CT or MRI scans. One hundred thirteen adrenal masses (75 unilateral and 19 bilateral; size range, 0.8– 4.7 cm) were evaluated in 94 patients. PET findings were inter-preted as positive if the 18F-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. Results: PET findings were positive in 71 ad-renal masses. Sixty-seven of these were eventually considered to be metastatic adrenal disease. In the remaining 4, no changes in lesion size were noted on follow-up examinations. PET findings were negative in 42 adrenal masses, of which 37 eventually proved to be benign. Among the 5 adrenal masses that were false-negative, one was a large necrotic metastasis; 1 was a 2.4-cm lesion with central hemorrhaging, and the remain-ing 3 were lesions of less than 11 mm. The sensitivity, specific-ity, and accuracy for detecting metastatic disease were 93%, 90%, and 92%, respectively. Conclusion: 18F-FDG PET is an accurate, noninvasive technique for differentiating benign from metastatic adrenal lesions detected on CT or MRI in patients with lung cancer. In addition, PET has the advantage of assess-ing the primary cancer sites and detecting other metastases. Key Words: 18F-FDG PET; lung cancer; adrenal masses; CT; adrenal metastase