Effect of Lenvatinib on a Patient with Medullary Thyroid Carcinoma Liver Metastasis Caused by Multiple Endocrine Neoplasia Type 2A.

A 61-year-old female was diagnosed with multiple endocrine neoplasia type 2A (MEN2A), caused by a heterozygous point mutation in the RET gene (TGC to TAC at codon 634) resulting in the substitution of cytosine with leucine (C634Y). The patient had pheochromocytoma (PCC) in the left adrenal gland and medullary thyroid carcinoma (MTC) with liver metastasis. Primary hyperparathyroidism (PHP) was not evident. Family history data suggested that the RET gene mutation was inherited from the father. The PCC was removed laparoscopically, but the MTC was observed conservatively for 7 years because the status of the MTC was compatible with T1N1M1 and stage IVC; therefore, it was not curable with surgery. The MTC liver metastasis increased in size. Lenvatinib, an oral multi-tyrosine kinase inhibitor, was administered until the patient had received a total dose of 1336mg, and then administration was stopped because of nausea. The reduction rate of the MTC liver metastasis was 31%, which was considered partial response. At this point, the patient was doing well, suggesting that lenvatinib was effective in treating the MTC liver metastasis and may be one of the treatment for advanced MTC caused by C634Y mutation in the RET gene.