Radiolabeled Molecules for Medullary Thyroid Cancer

Medullary thyroid carcinomas can also be located by scintigraphy with 111In-DTPA (diethylenetriamine pentaacetic acid) -octreotide. In some studies, there is a sensitivity for the detection of these tumors by this method, 50-70%. The relationship of calcitonin and carcinoembryonic antigen levels were significantly higher in patients in whom scintigraphy was performed with 111In-DTPA-octreotide. This implies that somatostatin receptors can be detected "in vivo" for different forms of medullary thyroid carcinoma Based on the specific binding of the analogs of somatostatin receptors present on the membrane of some tumors such as medullary thyroid been possible to devise a therapy to target-directed using both beta-emitting radionuclides (which have therapeutic properties) coupled to such molecules. The main radiopharmaceuticals used for this purpose are currently 177 Lu-DOTA-Tyr3-OCTREOTATE or 90Yttrium-DOTA]-TOC.

The medullary thyroid carcinoma (MTC) is a rare neuroendocrine tumor, accounting for only 4.9% of total thyroid carcinomas, however, compared to well differentiated carcinoma, presents a worse prognosis. The tumor staging, and restaging is essential since surgery is the only curative method. Elevated plasma concentrations of calcitonin (CT) and / or high levels of carcinoembryonic antigen (CEA), biochemical markers of MTC, suggest the presence of residual malignant disease / recurrence or metastasis at a distance. After surgery aggressive 40% of patients have persistent disease and about 10%, with undetectable post-surgery CT, develop tumor recurrence. At this point the therapeutic options are scarce and not available in our area. Although the investigators use the structural radiological study using ultrasound, computed tomography and magnetic resonance imaging for staging of the disease, they do not provide functional information. In this context, nuclear medicine examinations can add data such as growth potential and expression pattern of receptors for diagnostic and therapeutic purposes. In 2007, Ong SC. et al. Showed that 18 FDG PET / CT have the ability to detect residual disease, recurrent or metastatic disease with a sensitivity of 78% but only when calcitonin is up 1000pg/ml. Already Iten et al. Using the principle that these tumors express receptors for the somatostatin used OctreoScan ® and subsequent treatment with 90Yttrium-DOTA]-TOC showing not only an advantage for the location of the disease and the possibility of making an image guided therapy by. These authors also demonstrated a clinical benefit to the extent that 25% of the patients showed reduced calcitonin. The investigators hypothesized that those tumors may respond to 177-Lu-DOTA Tyr3-octreotate.