Real-world study of lenvatinib in patients with radioiodine‑refractory thyroid cancer treated in a tertiary reference center.

[INTRODUCTION] Radioiodine-refractory differentiated thyroid cancer (RAIR DTC), although rare, constitutes a real clinical challenge due to its prognosis despite a growing number of available treatment modalities. This study aimed to analyze the real-world efficacy and toxicity of lenvatinib therapy in a group of Polish patients with advanced RAIR DTC.

[MATERIAL AND METHODS] A group of 27 patients was eligible for lenvatinib therapy due to measurable, progressive, RAIR DTC, of whom 21 ultimately received the treatment. Treatment outcomes were assessed in terms of Response Evaluation Criteria in Solid Tumors (RECIST) as well as Kaplan-Meier estimates of overall survival and progression-free survival (PFS) for the whole cohort and for subgroups receiving lenvatinib as the first or subsequent line of targeted therapy. PFS was reported using both intention-to-treat (ITT) and per-protocol (PP) definitions, depending on whether treatment discontinuation was treated as censoring. Treatment toxicity was evaluated according to Common Terminology Criteria for Adverse Events (CTCAE).

[RESULTS] Median overall survival (OS) in the whole group was 38.9 months [95% confidence interval (CI): 23.8- not reached (NR)], while one-year and two-year survival rates were 0.85 (95% CI: 0.72-1.00) and 0.63 (95% CI 0.45-0.89), respectively. ITT-PFS was 21.3 months (95% CI: 12.2-NR). One-year ITT-PFS was 0.75 (95% CI: 0.57- .00), while 2-year ITT-PFS was 0.44 (95% CI: 0.22-0.76). Similar estimates were obtained using the PP-PFS definition. All patients reported treatment-related side effects, the most common being proteinuria, weight loss, hypertension, and mucositis.

[CONCLUSION] This retrospective analysis of a Polish RAIR thyroid cancer cohort demonstrated very good efficacy of lenvatinib in the first-line setting, while its activity in the second-line setting, although still present, was reduced. Based on these results, we suggest that lenvatinib should again be available for the treatment of RAIR thyroid cancer in Poland.