Endocrine Abstracts (2009) 20 OC1.3

131I-Iodometomidate radiotherapy for metastatic adrenocortical carcinoma: first clinical experience

Stefanie Hahner1, Michael Kreissl2, Martin Fassnacht1, Sarah Johanssen1, Heribert Haenscheid2, Christoph Reiners2, Bruno Allolio1 & Andreas Schirbel2

1Endocrine and Diabetes Unit, Department of Internal Medicine I, Wuerzburg, Germany; 2Department of Nuclear Medicine, Wuerzburg, Germany.

Subject: Treatment options for adrenocortical carcinoma (ACC) are still unsatisfactory. We could recently demonstrate that several patients with ACC exhibit a high and specific uptake of 123I-Iodometomidate (123I-IMTO). Therefore, we investigated if 131I-IMTO holds potential for radiotherapy in ACC.

Methods: Dosimetry with 40 MBq I-131-IMTO was performed over 5 days in 7 patients and calculated activities were administered on a compassionate use basis in 6 patients with ACC.

Results: Follow up data are available in 3 patients so far. The bone marrow proved to be the critical organ. Postulating that the bone marrow dose does not exceed a tolerable dose of 2 Gy, high therapeutic activities of up to 20 GBq were calculated. Patients received between 7 and 20 GBq 131I-IMTO as treatment dose. A high and lasting uptake was observed in almost all metastases. Corresponding to the values calculated from dosimetry, tumour doses up to 41.3 Gy were reached. Elimination of I131-IMTO from whole body showed a half life of 20 h. In all patients treatment was very well tolerated. Transient thrombocytopenia and leucopenia was observed in most patients. At follow up patient 1 showed a decrease of the size of those lesions that had shown tracer uptake. Patient 2 demonstrated a lasting decrease in F18FDG-uptake, however metastatic lesions slightly increased in size. Patient 3 had stable disease after 10 weeks follow up.

Conclusions: This is the first report of radiotreatment of metastatic ACC with 131I-IMTO. Due to the high specificity of tracer uptake high activities can be achieved within the target tissue, comparable to those achieved by other radionuclide treatment regimens. Treatment is well tolerated. However, this method has to be further evaluated to better estimate its clinical value in treatment of ACC.

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