Salvage Lenvatinib Therapy in Metastatic Anaplastic Thyroid Cancer

Background: Historical anaplastic thyroid cancer (ATC) outcomes have been terrible, with a median survival of only five months and < 20% one-year survival. Improved outcomes are now achieved with aggressive initial therapy in stages IVA and IVB disease, but patients with distant metastatic disease (stage IVC) still do poorly; improved therapies are sorely needed. Kinase inhibitors have emerged as promising agents in the therapy of advanced medullary and differentiated thyroid cancer, but there are limited data regarding the use of lenvatinib in ATC. The aim of this study was to delineate clinical outcomes in a series of patients with advanced ATC in response to lenvatinib therapy. Methods: A retrospective analysis was conducted involving all lenvatinib-treated Mayo Clinic ATC patients in 2015. Results: Of 28 distinct ATC patients seen in 2015, three (11%) with metastatic disease of ECOG performance status 2-3 were treated with lenvatinib. Two patients were male; age range at ATC diagnosis was 57-84 years. All three patients attained successful local control of their disease with surgery and/or combined chemoradiotherapy. Lenvatinib was offered as the second, third, or fourth line of therapy at the time of metastatic disease progression. Two patients incurred minor responses to therapy, with structural regression of distant metastatic tumor disease soon after starting lenvatinib treatment (at one to two months), while one patient achieved stable disease, but no Response Evaluation Criteria In Solid Tumors partial responses resulted. Overall survival after starting lenvatinib was two, six, and seven months. Fatigue and hypertension were prominent, and one patient developed pulmonary emboli while on lenvatinib. Conclusion: This initial single-institution experience suggests that lenvatinib may have some disease-modifying activity in metastatic ATC that is otherwise refractory to cytotoxic chemotherapy. Unfortunately, observed benefits were transient, and toxicities were prominent. Clinical trials are required to ascertain better the utility of lenvatinib in the management of advanced ATC.