[123I]Iodometomidate imaging in adrenocortical carcinoma: Evaluation of 58 patients

Objectives The new radiotracer [123I]iodometomidate (IMTO) facilitates adrenocortical imaging by selective binding to 11-beta-hydroxylase and aldosterone synthase. The clinical utility of IMTO imaging in adrenocortical carcinoma (ACC) was evaluated.

Methods 58 patients with histologically confirmed ACC all ENSAT stage IV (metastatic disease) received about 180 MBq IMTO. Sequential planar whole body scans until 24 hours p.i. and SPECT/CT hybrid imaging 4 - 6 h p.i. were performed. Uptake of IMTO in ACC lesions known from conventional imaging was assessed. Uptake characteristics were correlated with hormone secretion and previous treatments. We also determined how many patients were potentially suitable for targeted radionuclide therapy using [131I]IMTO.

Results Of the 430 lesions detected by conventional imaging, 30% showed strong, 8% moderate and 62% no tracer accumulation. 12 additional lesions were found by IMTO in 6 patients. 34 of the 58 (59%) patients had at least one IMTO-positive lesion. Cortisol and aldosterone secretion by ACC was positively correlated to IMTO uptake; cytotoxic chemotherapy and mitotane treatment did presumably not influence tracer uptake. 21 patients (36.2%) had radiotracer uptake in all lesions ≥ 2 cm and therefore were potential candidates for targeted systemic radiotherapy with [131I]IMTO.

Conclusions IMTO detected both primaries and metastatic lesions of ACC. However, a substantial percentage of lesions failed to show IMTO uptake. About one third of all ACC patients with metastastic may qualify for a treatment with [131I]IMTO, the first molecular informed therapy for advanced ACC.

Research Support Wilhelm Sander Foundation (Grant No. 2003.175.2)