Efficacy and Limitations of Lenvatinib Therapy for Radioiodine-Refractory Differentiated Thyroid Cancer: Real-World Experiences

Background: The ultimate clinical goal of advanced cancer treatment is improvement of survival. Tyrosine kinase inhibitors (TKIs) were recently approved for radioiodine-refractory differentiated thyroid carcinoma (RR-DTC) that is resistant to conventional therapies since they have significant potential to improve survival in patients who previously had no more treatment strategies available. However, eligible patients are limited in clinical practice, making it difficult to accurately determine the efficacy of TKIs. Patients and Methods: We retrospectively analyzed the efficacy of lenvatinib at a single institution, enrolling 42 RR-DTC patients. Results: The best overall response was partial remission in 26 (62%) patients, stable disease in 10 (24%) patients, and progressive disease (PD) in 6 (14%) patients. The results indicated three-year overall survival (OS) and progression-free survival rates of 51.0% and 32.4%, respectively. Twenty-three (55%) patients had backgrounds that did not match the inclusion criteria of the Study of (E7080) Lenvatinib in Differentiated Cancer of the Thyroid (SELECT) trial. Furthermore, PD-experienced patients individually decided whether to continue lenvatinib, and 17 (41%) made the decision themselves; these patients had a three-year OS of 43.0% and postprogression survival (PPS) of 13.3 [95% confidence interval 6.1-not reached] months. Conclusions: Our real-world investigation revealed that patients have wide-ranging background characteristics, and the decision regarding continuation of therapy after PD is based on the patient's general condition. Our management protocol resulted in good PPS. Furthermore, our results indicated equivalent efficacy of lenvatinib as in the SELECT trial. In conclusion, lenvatinib proved effective for RR-DTC patients in a real-world setting.