Exploratory analysis of prognostic factors for lenvatinib in radioiodine-refractory differentiated thyroid cancer.

Background: Multitarget kinase inhibitors (m-TKI), including lenvatinib, are now available as treatment options for radioiodine-refractory differentiated thyroid cancer (RR-DTC). However, the optimal timing of treatment initiation with m-TKI in these patients remains to be defined.

Methods: We retrospectively reviewed the clinical records of 30 consecutive patients with RR-DTC. The relationship between clinical characteristics was evaluated, including tumor growth parameters at pretreatment/post-treatment and efficacy of lenvatinib.

Results: A total of 26 patients with RR-DTC treated with lenvatinib were evaluable for response and eligible for analysis. From the results of multivariate analysis, baseline tumor size and tumor-related symptoms were independent negative prognostic factors for overall survival (OS) and progression-free survival (PFS). Pretreatment tumor growth parameters were not prognostic for either PFS or OS.

Conclusions: Patients with RR-DTC with a high tumor burden and tumor-related symptoms had significantly worse prognosis. Greater tumor reduction after starting lenvatinib may lead to better prognosis, irrespective of pretreatment high tumor growth rate.