A Case of Advanced Medullary Thyroid Carcinoma Successfully Treated with Sunitinib

Context. Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor arising from "C" cells of the thyroid; it is a RET associated cancer that can be sporadic or familial in origin. Advances in understanding the genetic changes associated with the development of MTC explain the growing interest in the therapeutic potential of tyrosine kinase inhibitors. Sunitinib is an orally administered multikinase inhibitor likely to target multiple pathways in the tumor, stromal, and endothelial compartments. Its role in the treatment of MTC patients has not yet been established. Objective. To present the case of a patient with a sporadic and unresectable MTC who was successfully treated with sunitinib. Patient and Results. A 55-year-old man with locally advanced MTC, without germinal and/or somatic RET mutations, was started on sunitinib (50 mg/day for 28 days, followed by 14 days of no treatment). At the time of writing, he had received four consecutive cycles. At the end of the first cycle, his serum calcitonin level had dropped by 81%. In the following cycles, a long-lasting minor response was observed. An early and dramatic tumor reduction, particularly of a cervical lymph node conglomerate, was observed and confirmed by the Response Evaluation Criteria in Solid Tumors. Conclusion. Sunitinib may play a role in the management of patients with locally advanced MTC or distant metastatic disease, for which no effective systemic therapy exists. Moreover, the absence of RET mutations does not seem to be an exclusion criterion for sunitinib treatment. The Oncologist 2009;14:1083-1087