Fluorodesoxyglucose uptake in the remaining adrenal glands during the follow-up of patients with adrenocortical carcinoma: Do not consider it as malignancy

Objective: To make the specificity of fluorodesoxyglucose ( ¹⁸FDG) positron emission tomography (PET) precise, in the follow-up of patients with adrenal cancer. Design: This single centre retrospective study assessed the frequency and outcome of ¹⁸FDG uptake in the remaining adrenal glands after adrenalectomy for adrenocortical carcinoma (ACC) or malignant phaeochromocytoma (PH). Results: Two hundred and ten ¹⁸FDG PET scans in 62 ACC patients, all under 1,ortho-1,para′-dichlorodiphenyl- dichloro-ethane (o,p′-DDD) treatment, and 30 ¹⁸FDG PET scans in 8 PH patients were reviewed. Abnormal ¹⁸FDG uptake in the remaining adrenal glands was found in 19 (8%) ¹⁸FDG PET scans, in 10 (16%) ACC patients and in none of the PH patients. ¹⁸FDG uptake was found in 4% of the patients before the onset of o,p′-DDD, in 29% of the patients 0-6 months after the onset of o,p′-DDD (P = 0.05), in 26% of the patients 6-12 months (P = 0.072) after the onset of o,p′-DDD and in 14% of the patients 12-24 months after the onset of o,p′-DDD. It was never found later than 24 months after the onset of o,p′-DDD. Adrenal glands with ¹⁸FDG uptake were normal on computed tomography scans with i.v. contrast agent in all cases. ¹⁸FDG uptake in the remaining adrenal glands decreased and disappeared on subsequent FDG PET imaging in eight of the patients with follow-up available. Conclusions: ¹⁸FDG uptake in the remaining adrenal glands occurred in 14-29% of the patients followed for ACC within 24 months after adrenalectomy and onset of o,p′-DDD. This uptake is transient and should not be considered as suspicious for malignancy.