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 ((18)FDG) 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 (18)FDG uptake in the remaining adrenal glands after adrenalectomy for adrenocortical carcinoma (ACC) or malignant phaeochromocytoma (PH).

RESULTS: Two hundred and ten (18)FDG PET scans in 62 ACC patients, all under 1,ortho-1,para'-dichloro-diphenyl-dichloro-ethane (o,p'-DDD) treatment, and 30 (18)FDG PET scans in 8 PH patients were reviewed. Abnormal (18)FDG uptake in the remaining adrenal glands was found in 19 (8%) (18)FDG PET scans, in 10 (16%) ACC patients and in none of the PH patients. (18)FDG 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 (18)FDG uptake were normal on computed tomography scans with i.v. contrast agent in all cases. (18)FDG uptake in the remaining adrenal glands decreased and disappeared on subsequent FDG PET imaging in eight of the patients with follow-up available.

CONCLUSIONS: (18)FDG 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.