Background: Although lenvatinib is the preferred treatment for unresectable radioactive iodine-refractory differentiated thyroid cancer (RR-DTC), this agent exerts considerable toxicities, which can lead to frequent dose interruptions and modifications. The adoption of planned drug holidays has been recently suggested as one means of minimizing or avoiding these severe adverse events. Our retrospective study demonstrated that planned drug holidays appear to be a promising strategy for continuing of lenvatinib. However, the benefits of planned drug holidays in a prospective study have yet to be clarified. Here, we investigated the impact of planned drug holidays on clinical outcomes in patients treated with lenvatinib in the COLLECT study. Methods: In COLLECT, a prospective observational study, patients with RR-DTC were treated with lenvatinib in a real-world clinical setting. Lenvatinib was administered orally at a dose of 24 mg daily. Dose modification for toxicities was permitted. Furthermore, planned drug holidays were allowed to avoid severe or intolerable toxicities. The present post hoc analysis focused on evaluating the impact of planned drug holidays on clinical outcomes, including overall survival (OS), time to treatment failure (TTF), time to failure strategy (TFS), and progression-free survival (PFS), in patients in the COLLECT study who were treated with lenvatinib. Results: In total, 262 patients were included. Of the 253 patients evaluable for efficacy, 73 undertook a planned drug holiday at the discretion of the attending physician. OS, TTF, TFS, and PFS were significantly longer in patients who used a planned drug holiday than in those who did not. The planned drug holiday group demonstrated notable clinical outcomes, with a 1-year OS of 95.8% and a 1-year PFS of 94.5%. Moreover, planned drug holidays demonstrated a clinically meaningful advantage in clinical outcomes. The planned drug holiday group had a significantly longer duration of administration at a dose of ≥10 mg. Conclusions: Planned drug holidays for lenvatinib were associated with significantly improved clinical outcomes compared to daily oral administration. Further investigation of the optimal treatment schedule for lenvatinib is warranted. Clinical Trial Registration: UMIN000022243.
Keywords: differentiated thyroid cancer; lenvatinib; planned drug holiday; radioactive iodine-refractory.