Outcome of initial lenvatinib treatment in patients with unresectable anaplastic thyroid cancer.

Anaplastic thyroid cancer (ATC) is a very rare disease with a poor prognosis and with no established effective drug therapy. The present study aimed to report the outcomes of lenvatinib single-agent therapy as an initial drug treatment in ATC, and to investigate its safety and efficacy. This retrospective cohort study included 56 patients with unresectable primary ATC, of whom 36 were treated with lenvatinib and 12 with weekly paclitaxel, and 8 patients who refused any drug treatment who received palliative care. The average survival in the lenvatinib group was 5.8 months, which was significantly longer than 2.0 months in the paclitaxel group (P=0.005). The efficacy of lenvatinib in the 36 patients with ATC, whose primary tumors were unresectable, was evaluated. The response rate was 33% and the median overall survival time was 5.0 months. A safety review indicated that lenvatinib should be used under the careful observation of local findings. Two patients, who showed a reduction with lenvatinib, underwent conversion surgery, which prolonged the prognosis in terms of avoiding events, such as asphyxia, fistula and hemorrhage due to tumor growth; however, the surgical margins were positive, indicating that complete remission was impossible even if surgical resection was performed. Therefore, starting with lenvatinib treatment and identifying a therapeutic drug based on genomic analysis is an acceptable treatment strategy for ATC while halting the disease progression.