Nuclear Medicine & Radiation Therapy

SPECT-CT Modality for Imaging of Medullary Thyroid Cancer (MTC)

Abstract

Sonya Sergieva, Mariana Atanasova and Ivan Terziev

Medullary thyroid cancer (MTC) is a neuroendocrine tumor that arises from the parafollicular Calcitonin-producing C-cells of the thyroid. Typically the MTC is an extremely slow-growing cancer; however, it has a tendency of spreading distant metastases fairly early. Systemic chemotherapy and external been radiotherapy have not shown to give a good MTC response. As of date radical thyroidectomy is the main method of choice for therapy. New compounds like tyrosine kinase inhibitors (TKIs) targeting signaling pathways may have a positive outcome and be of great clinical benefits in patients with advanced and metastatic MTC. Somatostatin receptor are over expressed in MTC and thus allows the use of radiolabeled somatostatin analogues for scintigraphic imaging before and after treatment for proper staging and follow-up of these patients. SPECT-CT is used to optimize somatostatin-receptor scintigraphic protocols for MTC imaging. We have presented a case report of a patient who underwent total thyroidectomy with bilateral lymphadenectomy in August 2006 due to the diagnosed MTC. This patient was treated by chemotherapy and surgery during the period between January/2007- December/2014 because of the recurrent disease. In December 2014 the calcitonin level reached 56 000 pg/ml; whole body scan with 740 MBq 99mTc-EDDA/HYNIC-TOC, followed by target SPECT-CT showed a total disease progression with advanced metastatic dissemination into the body. The assigned therapy was with Caprelsa®(Vandetanib) 300 mg/d orally which was initialized from March 2015 until present. In June 2016 a control SPECT-CT somatostatinreceptor scintigraphy with 740 MBq 99mTc-Tektrotyd was performed from which was reported a partial disease response with a reduction of about 60% in size and a decrease in the number of metastatic lesions shown to correlated with the decreased calcitonin level up to 1560 pg/ml. It can be concluded that SPECT-CT with 99mTc- Tektrotyd has important clinical role for re-staging and follow-up of patients with recurrent and metastatic MTC after target therapy.