Rapid response of hypercortisolism to vandetanib treatment in a patient with advanced medullary thyroid cancer and ectopic Cushing syndrome.

Medullary thyroid carcinoma (MTC) may rarely present with paraneoplastic syndromes. Among the most frequent ones are the appearance of diarrhea and ectopic Cushing syndrome (ECS). The ECS in the context of MTC is usually present in patients with distant metastatic disease. The use of drugs such as ketoconazole, metyrapone, somatostatin analogs and etomidate have been ineffective alternatives to control hypercortisolism in these patients. Bilateral adrenalectomy is often required to manage this situation. Recently, the use of tyrosine kinase inhibitors has been shown to be a useful tool to achieve eucortisolism in patients with metastatic MTC and ECS. We present a patient with sporadic advanced persistent and progressive MTC with lymph node and liver metastases, which after 16 years of follow-up developed an ECS. After one month of 300 mg/day vandetanib treatment, a biochemical and clinical response of the ECS was achieved but it did not result in significant reduction of tumor burden. However the patient reached criteria for stable disease according to response evaluation criteria in solid tumors (RECIST 1.1) after 8 months of follow-up.