Double agent radionuclide therapy for differentiated thyroid cancer with bone metastases: the first experience of simultaneous administration of ¹³¹I and ¹⁵³Sm-EDTMP

About 12,000 new cases of differentiated thyroid cancer (DTC) are registered in Russia annually. The majority of cases have good prognosis after surgery with or without subsequent radioiodine therapy (RIT). The presence of distant metastases, especially bone metastases, and advanced age worsens the prognosis even in cases with high radioiodine (RI) uptake. Usually bone metastases are painful, requiring analgesics. Bone seeking radiopharmaceuticals may be useful as well as RIT for patients with bone metastases. For this group of patients may be useful double agent radionuclide therapy (DART) with sequential administration of ¹⁵³Sm-EDTMP and RI. 28 DTC patients (18 women and 10 men) with bone or bone and lung metastases were treated this way since 2009. Age ranged from 33 to 76 years (average 56±2.3). In the majority of cases ¹⁵³Sm-EDTMP was administered firstly, the next day after bone scan and SPECT/CT RI was administered with following SPECT/CT. DART (¹⁵³Sm- EDTMP + RI) was applied from 1 to 10 times in each case (6±2). It was well tolerated; no significant bone marrow suppression or any other adverse events were observed. Marked reduction of pain or its complete disappearance and stabilization of bone metastases was achieved in all cases. In cases of progression disease RIT stopped, the treatment followed with sorafenib or lenvantinib and ¹⁵³Sm-EDTMP if it's necessary. Thus, DART (¹⁵³Sm- EDTMP + RI therapy) demonstrated good palliative and cytotoxic effect without increase toxicity. (author)