[¹²³I]Iodometomidate imaging in adrenocortical carcinoma

Imaging with [¹²³I]iodometomidate ([¹²³I]IMTO) has been shown to diagnose adrenocortical lesions with high sensitivity and specificity.

Our objective was to evaluate the clinical utility of [¹²³I]IMTO imaging in adrenocortical carcinoma (ACC).

We conducted a prospective monocentric diagnostic study and a prospective case series at a single tertiary referral center.

Fifty-eight patients with histologically confirmed ACC, all European Network for the Study of Adrenal Tumors stage IV (with distant metastases), received 185 MBq [¹²³I]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.

Outcome measures included uptake of [¹²³I]IMTO in ACC lesions, sensitivity and specificity of [¹²³I]IMTO imaging compared with conventional imaging, and number of patients eligible for [¹³¹I]IMTO therapy.

Of 430 lesions detected by conventional imaging, 30% showed strong, 8% moderate, and 62% no tracer accumulation. [¹²³I]IMTO detected both primary and metastatic lesions of ACC. However, a substantial percentage of lesions failed to show [¹²³I]IMTO uptake. The overall sensitivity and specificity values were 38% and 100%, respectively. Thirty-four patients (59%) had at least 1 [¹²³I]IMTO-positive lesion. Cortisol and aldosterone secretion by ACC was positively correlated to [¹²³I]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 [¹³¹I]IMTO.

About one-third of patients with ACC show specific retention of [¹²³I]IMTO in metastatic lesions. This study provides support for the conduct of a prospective trial to determine whether the first molecular informed therapy using [¹³¹I]IMTO will be of value to patients with metastatic ACC.