Receptor Radionuclide Therapy with 90Y-DOTATOC in Patients with Medullary Thyroid Carcinomas

Metastatic medullary thyroid cancer (MTC) shows a progressive course. Surgery is the only curative treatment. In advanced disease, chemo- and radiotherapy show poor results. Newly developed somatostatin analogue [DOTA ⁰,Tyr³]octreotide (DOTATOC) labeled to ⁹⁰Y is administered in patients with endocrine tumors expressing somatostatin receptors, like MTC. Preliminary studies demonstrated that ⁹⁰Y-DOTATOC could be safely administered, resulting in objective responses in 27% of patients. Aims: To evaluate the efficacy of ⁹⁰Y-DOTATOC therapy in metastatic MTC patients with positive OctreoScan, progressing after conventional treatments. Twenty-one patients were retrospectively evaluated after therapy, receiving 7.5-19.2 GBq in 2-8 cycles. Results: Two patients (10%) obtained a complete response (CR), as evaluated by CT, MRI and/or ultrasound, while a stabilization of disease (SD) was observed in 12 patients (57%); seven patients (33%) did not respond to therapy. The duration of the response ranged between 3-40 months. Using biochemical parameters (calcitonin and CEA), a complete response was observed in one patient (5%), while partial response in five patients (24%) and stabilization in three patients (14%). Twelve patients had progression (57%). Complete responses were observed in patients with lower tumor burden and calcitonin values at the time of the enrollment. Conclusions: This retrospective analysis is consistent with the literature, regarding a low response rate in medullary thyroid cancers treated with ⁹⁰Y-DOTATOC. Patients with smaller tumors and higher uptake of the radiopeptide tended to respond better. Studies with ⁹⁰Y-DOTATOC administered in earlier phases of the disease will help to evaluate the ability of this treatment to enhance survival. New more specific peptides and new isotopes will also represent the key of a better treatment of MTC.