Neoadjuvant Lenvatinib in Advanced Unresectable Medullary Thyroid Carcinoma: A Case Report

ABSTRACT Objective Medullary thyroid carcinoma, a rare form of thyroid cancer, is typically managed with surgical excision. However, in patients with locally-invasive tumors, an aggressive surgical attempt may result in unnecessary morbidity. Neoadjuvant tyrosine kinase inhibition has been utilized to downstage tumors prior to surgical excision but its role in thyroid cancer treatment is not well-established. We describe the potential role that lenvatinib, a tyrosine kinase inhibitor, may have as a neoadjuvant agent in advanced locoregional medullary thyroid carcinoma. Methods Our patient presented with a large left thyroid mass and bulky left lateral neck lymphadenopathy. Imaging studies revealed a hypervascular and locally-invasive tumor with metastatic central and left lateral lymphadenopathy. A lymph node biopsy cytologic evaluation and plasma calcitonin concentration of 32,926 pg/mL were consistent with medullary thyroid carcinoma. Rearranged during transfection germline mutation testing was negative. A multidisciplinary team of physicians deemed the patient a poor surgical candidate and recommended 4 months of neoadjuvant lenvatinib therapy to reduce tumor burden with a subsequent reassessment of resectability. Given the tumor's hypervascularity, lenvatinib was chosen due its potent vascular endothelial growth factor receptor inhibition, as well as its availability at our institution. Results Lenvatinib therapy resulted in rapid regression of tumor volume (approximately 70% reduction) as documented by computed tomography and ultrasound. Surgery after 4 months of treatment resulted in a 99% reduction in serum calcitonin and imaging studies 6 months later showed no residual disease. Conclusion Lenvatinib has potential as a neoadjuvant agent in advanced medullary thyroid carcinoma, and permitted tumor resection in this previously inoperable patient.