Low-Dose Continuation of Lenvatinib for the Treatment of the Patients with Unresectable Thyroid Carcinoma

Abstract Background Lenvatinib, a multi-tyrosine kinase inhibitor (TKI), has been proven to be an effective treatment option for patients with unresectable thyroid carcinoma. However, it causes certain adverse effects (AEs), and discontinuation or dose reduction of the drug is almost unavoidable. Few studies have investigated the impact of the length, dose, or interruption of lenvatinib administration on the prognosis of patients with unresectable thyroid carcinoma. Here, we aimed to verify the significance of our efforts to continue lenvatinib therapy to the longest duration possible with a reasonable daily dose and minimum discontinuation period in patients with unresectable thyroid carcinoma. Methods The clinical records of 42 patients with unresectable thyroid carcinoma treated with lenvatinib between 2015 and 2020 were retrospectively studied. Results The Cox proportional hazard model-based analysis indicated that the overall survival (OS) of patients treated with a mean dose of lenvatinib <8 mg/day was significantly better than that of those treated with 8-24 mg/day (hazard ratio (HR)=0.38, 95% confidence interval (CI): 0.03-4.99 for 1.14-4.54 mg/day, and HR=0.01, 95% CI: 0.00-0.13 for 4.56-7.97 mg/day) adjusted for various factors (sex, age, length of drug interruption, and so on). The cumulative administration dose of lenvatinib tended to be higher in patients treated with low doses (<8 mg/day) than in those treated with relatively high doses (8-24 mg/day). Conclusion Considering its AEs, continuation of lenvatinib administration with an adequate daily dose with drug interruption may be important for prolonging survival of patients with unresectable thyroid carcinoma.