Adrenal Findings in FDG-PET– Analysis of a Cohort of 1021 Patients From a Cancer Center

Abstract Purpose: The use of FDG-PET/TC for cancer staging has been leading to the increasing diagnosis of adrenal lesions, which usually represent a clinical challenge. Our aim was to characterize the adrenal lesions found in FDG-PET of patients followed in a cancer center.Methods: Retrospective analysis of all FDG-PET studies performed in our center in the last 10 years. Exams reporting adrenal lesions in the CT component and/or anomalous adrenal FDG uptake were selected. Cases were characterized regarding clinical, laboratorial, imaging and pathological findings. Results: We identified 27,427 FDG-PET studies. Of those, 7.6% evidenced adrenal findings. We included 1364 exams corresponding to 1021 patients. Only 15.6% were referred to the endocrinology department and 38% of the lesions were not studied.Malignant lesions were present in 38.9% of the studied patients: metastases in 37.5%, carcinoma in 1.2% and other malignant tumors in 0.4%. Median SUVmax of malignant lesions was significantly higher than the SUVmax of the benign findings (p<0.05). We also observed a higher median SUVmax in adrenal metastases than in adenomas (p<0.05). There was a tendency for higher SUVmax of adrenal carcinomas when comparing with other malignant lesions (p=0.066). The median SUVmax was not different between pheochromocytomas and other tumors (p>0.05). Conclusion: Occult adrenal lesions discovered during FDG-PET/CT are common in cancer context and are frequently benign. SUVmax may be a useful tool in the workup of adrenal lesions but with several important caveats.