Adrenal lesions: characterization with fused PET/CT image in patients with proved or suspected malignancy--initial experience

Abstract

Purpose: To retrospectively evaluate the accuracy of the fused positron emission tomographic (PET)/computed tomographic (CT) image for characterization of adrenal lesions in patients who have proved malignancy or are suspected of having malignancy.

Materials and methods: Institutional review board approval was received for this retrospective HIPAA-compliant study, and informed consent was waived. Forty-one adrenal lesions in 38 patients (21 men, 17 women; mean age, 66 years; range, 37-86 years) were evaluated with PET/CT. Of the 41 lesions, nine were assumed to be malignant with documentation of enlargement (n = 8) or reduction in size in response to treatment (n = 1), and 32 were assumed to be benign with documentation of stability for 6 months (n = 31) or with confirmation with biopsy results (n = 1). The PET examination findings were positive when adrenal lesion maximum standardized uptake values (SUVs) exceeded hepatic maximum SUVs. CT contrast medium washout analysis was used to further characterize two lesions with PET findings positive for malignancy. The t test was used to assess significant (P < .05) differences between fluorine 18 fluorodeoxyglucose (FDG) uptake of benign lesions and that of malignant lesions.

Results: At PET/CT, findings for all malignant lesions were positive (mean adrenal lesion-liver activity ratio, 4.04; range, 1.53-17.08). Of the 32 benign lesions, most (30 of 32) had activity less than that of the liver (mean ratio, 0.66; range, 0.22-0.94). PET/CT demonstrated sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 100%, 93.8%, 81.8%, 100%, and 95.1%, respectively. Incorporating contrast material-enhanced CT with delayed imaging increased specificity to 100% because two lesions with PET findings positive for malignancy were characterized as benign. There was a significant difference between maximum SUV (P < .05) and the ratio of adrenal lesion-liver FDG activity (P < .001) in benign versus malignant adrenal lesions.

Conclusion: PET/CT provides a powerful combination of functional and attenuation information for adrenal lesion characterization. All malignant lesions were detected at PET/CT, with no false-negative results.