Combined FDG-PET and 123I-Iodometomidate Imaging for Adrenal Neoplasia

Adrenal masses are highly prevalent and detected with high frequency by conventional imaging. Conventional imaging often fails to rule out a malignant lesion. Accordingly, most hormonally inactive adrenal masses removed by surgery are benign adenomas for which surgical removal is unnecessary and poses an avoidable risk to the patients. We hypothesize that the combination of FDG-PET and 123I-Iodometomidate imaging has the potential to noninvasively identify benign adrenocortical adenomas with high accuracy, thereby avoiding unnecessary surgery. Uptake of 123I-Iodometomidate by the adrenal mass demonstrates the presence of CYP 11B enzymes which specifically bind metomidate with high avidity establishing the adrenocortical origin of the lesion, while low uptake of FDG-PET in an adrenocortical lesion establishes its benign nature and excludes the presence of adrenocortical cancer (ACC). The proposed trial will assess the sensitivity, specificity, positive and negative predictive value of the combined imaging for the diagnosis of adrenocortical adenoma. A secondary focus is on the performance of the combined test for differentiating ACC from non-ACC lesions. We expect that the results of our trial will help to greatly reduce the need for surgery in hormonally inactive adrenal masses.

Histopathology of a surgically removed adrenal mass by an expert surgeon is considered to be the gold standard for the differential diagnosis of an adrenal neoplasia. Thus we will only recruit patients scheduled for surgery for an adrenal mass of uncertain origin. Patients will be eligible for the trial when an adrenal mass has been discovered and standard imaging (CT and/or MRI) has not led to a clear characterization of the malignant potential of the lesion (Hounsfield units in unenhanced CT ≥10). In addition, patients with adrenal neoplasia will be only recruited when a hormonally active lesion has been excluded and surgery is planned because of a perceived risk of malignancy. Patients will be evaluated by both \[123I\]Iodometomidate SPECT/CT and \[18F\]fluorodeoxyglucose PET/CT. Computed tomography will be performed as low dose CT of the adrenal region. Imaging can be started with either \[123I\]Iodometomidate SPECT/CT or \[18F\]fluoro- deoxyglucose PET/CT and can be performed at two consecutive days. The time interval between \[123I\]Iodometomidate SPECT/CT and \[18F\]fluorodeoxyglucose PET/CT should not exceed 6 weeks. Patients will have a follow up visit 2-4 weeks after \[123I\]Iodometomidate SPECT/CT and \[18F\]fluorodeoxyglucose PET/CT (or immediately before surgery, if earlier than 2 weeks post imaging). Thirty days after surgery patients will be contacted by phone for assessment of adverse events related to surgery.

Eligibility Criteria:
Inclusion Criteria:

* Patients with a solid indeterminate adrenal mass scheduled for surgery with a diameter \> 3 cm or an increase in tumour diameter after the initial evaluation of \> 1 cm during follow-up, age ≥30 years

Exclusion Criteria:

* Patient unfit or unwilling to undergo surgery, biochemical evidence of phaeochromocytoma, primary hyperaldosteronism or overt clinical Cushing's syndrome