# Therapeutic Efficacy of a Very Low/Low Dose of Lenvatinib in Advanced Radioiodine-Refractory Thyroid Cancer: A Real-World Series from a Single Center

## TL;DR

This study shows that using very low or low doses of lenvatinib can effectively manage advanced thyroid cancer while reducing severe side effects.

## Contribution

The paper presents real-world evidence of lenvatinib's efficacy and safety at very low/low doses for fragile RAI-RTC patients.

## Key findings

- 53.3% of patients did not show disease progression.
- 26.6% of patients achieved a partial response with tumor volume reduction.
- 80% of patients experienced adverse events, mostly of moderate severity.

## Abstract

Managing the treatment of advanced RAI-RTC (advanced radioiodine-refractory differentiated thyroid cancer) with progressive disease remains a clinical challenge in the presence of comorbidities or locally advanced (with invasion of the trachea, the esophagus, and/or the carotid artery) and unresectable or metastatic progressive tumors. Initiating lenvatinib at a low or very low intensity in these patients seems to be a promising approach, balancing effective disease control with a favorable safety profile. The aim of our paper is to describe the therapeutic efficacy and safety of a very low (4 mg/day) or low (4–10/day) lenvatinib dose in 15 patients with RAI-RTC. In our experience, lenvatinib, even at very low doses, can achieve significant tumor reduction and extend progression-free survival, all while minimizing severe adverse effects.

Background: Lenvatinib is a receptor tyrosine kinase inhibitor indicated for advanced radioiodine-refractory thyroid cancer (RAI-RTC). It is recommended to start at 24 mg per day; however, in patients who are at risk of severe adverse events, it may be reasonable to start at lower doses. Patients and Methods: We included 15 patients with RAI-RTC who started lenvatinib at a very low/low dose and evaluated the efficacy and safety. Results: Eight patients (53.3%) did not show progression of the disease, and about half of the patients (53.3%) were alive at the last follow-up visit. Up to 26.6% of patients achieved a partial response to therapy, with a notable volume reduction in the local and metastatic lesions. However, 80% of patients experienced adverse events, mainly of a moderate grade. Conclusions: Although these findings are based on a small sample size and a single-center study, treatment with lenvatinib at very low/low doses in fragile patients seems to be a promising strategy for the management of RAI-RTC, balancing effective disease control with a favorable safety profile.