LAUSR

Background/Aim: Lenvatinib is standard therapy for radioiodine-refractory differentiated thyroid cancer (RR-DTC), although the optimal timing for starting treatment is still controversial. The aim of this study was to evaluate the prognostic impact of baseline tumour size (BTS) in patients with RR-DTC treated with lenvatinib. Patients and Methods: Fifty-one RR-DTC patients who had at least one measurable lesion and treated with lenvatinib were retrospectively analysed. BTS was defined as the sum of the longest dimensions of all measurable target lesions. Results: Median progression-free survival (PFS) and overall survival (OS) in the larger BTS (≥42 mm) group were shorter than those in the smaller (<42 mm) group. This result was more significant in patients with fast-growing tumours. BTS was an independent prognostic factor for both PFS and OS. Conclusion: Starting lenvatinib at BTS <42 mm should be recommended to achieve good treatment outcomes in patients with RR-DTC.