Evaluation of adrenal masses in patients with bronchogenic carcinoma using ¹⁸F-fluorodeoxy-glucose positron emission tomography

OBJECTIVE. The purpose of this study was to assess the usefulness of positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (FDG) when differentiating benign from metastatic adrenal masses in patients with bronchogenic carcinoma. SUBJECTS AND METHODS. For our prospective study, any patient presenting to our institution with pathologically proven bronchogenic carcinoma and an adrenal mass was eligible. Thirty-three adrenal masses (mean size, 3 cm: range, 1-9 cm) in 27 patients were revealed by CT. PET was performed in all 27 patients and interpreted as positive when FDG uptake in the adrenal mass was greater than background activity or negative when FDG uptake in the adrenal mass was equal to or less than background activity. In addition, semiquantitative analysis was performed by computing a standardized uptake ratio. All studies were reviewed independently by three radiologists and then correlated with biopsy and CT findings. Specificity and sensitivity for determining metastatic disease to the adrenal gland were calculated. RESULTS. FDG uptake was positive (abnormally increased) in 25 adrenal masses. Twenty three (92%) of the 25 masses were metastatic disease. The mean standardized uptake ratio of these was 6.28 (range, 3.22-14.41). The remaining two masses (8%) that had positive FDG uptake showed no tumor at percutaneous biopsy. The standardized uptake ratio values for these two masses were 3.0 and 3.7. FDG uptake was negative (normal) in eight adrenal masses. All these lesions were benign as proven by biopsy (n = 2) and CT attenuation values of less than 10 H (n = 6). The mean standardized uptake ratio value for these eight lesions classified as benign was 1.77 (range, 0.93-3.70). The sensitivity for detecting metastatic disease was 100%, and the specificity was 80%. CONCLUSION. PET with FDG is an accurate, noninvasive way to differentiate benign from metastatic adrenal masses in patients with bronchogenic carcinoma.