[123I]Iodometomidate Imaging in Adrenocortical Carcinoma

Context: Imaging with [I-123]iodometomidate ([I-123]IMTO) has been shown to diagnose adrenocortical lesions with high sensitivity and specificity. Objective: Our objective was to evaluate the clinical utility of [I-123]IMTO imaging in adrenocortical carcinoma (ACC). Design: We conducted a prospective monocentric diagnostic study and a prospective case series at a single tertiary referral center. Patients and Interventions: Fifty-eight patients with histologically confirmed ACC, all European Network for the Study of Adrenal Tumors stage IV (with distant metastases), received 185 MBq [I-123]IMTO. Sequential planar whole-body scans until 24 hours post injection and single photon emission computed tomography/computed tomography (SPECT/CT) hybrid imaging 4 to 6 hours post injection were performed. Main Outcome Measures: Outcome measures included uptake of [I-123]IMTO in ACC lesions, sensitivity and specificity of [I-123]IMTO imaging compared with conventional imaging, and number of patients eligible for [I-131]IMTO therapy. Results: Of 430 lesions detected by conventional imaging, 30% showed strong, 8% moderate, and 62% no tracer accumulation. [I-123]IMTO detected both primary and metastatic lesions of ACC. However, a substantial percentage of lesions failed to show[I-123]IMTO uptake. The overall sensitivity and specificity values were 38% and 100%, respectively. Thirty-four patients (59%) had at least 1 [I-123]IMTO-positive lesion. Cortisol and aldosterone secretion by ACC was positively correlated to [I-123]IMTO uptake (P = .01); cytotoxic chemotherapy and mitotane treatment presumably did not influence tracer uptake. Twenty-one patients (36.2%) had radiotracer uptake in all lesions >= 2 cm and therefore were potential candidates for targeted systemic radiotherapy with [I-131]IMTO. Conclusion: About one-third of patients with ACC show specific retention of [I-123]IMTO in metastatic lesions. This study provides support for the conduct of a prospective trial to determine whether the first molecular informed therapy using [I-131]IMTO will be of value to patients with metastatic ACC.