Multi-kinase inhibitors for the treatment of asymptomatic radioactive Iodine-refractory differentiated thyroid cancer: Global non-interventional study (RIFTOS MKI)

[[abstract]]BACKGROUND: Sorafenib and lenvatinib are multi-kinase inhibitors (MKI) approved for patients with radioactive iodine-refractory (RAI-R) differentiated thyroid cancer (DTC). There is no consensus on when to initiate MKI treatment. The objective of this study was to evaluate time to symptomatic progression (TTSP) in patients with RAI-R DTC for whom the decision to treat with an MKI was made at study entry. METHODS: International, prospective, open-label, non-interventional cohort study (NCT02303444). Eligible patients had asymptomatic, progressive RAI-R DTC, with ≥1 lesion ≥1 cm in diameter and life expectancy ≥6 months. The decision to treat with an MKI was at the treating physician's discretion. Primary endpoint was TTSP from study entry. Two cohorts were evaluated: patients for whom a decision to initiate an MKI was made at study entry (Cohort 1) and patients for whom there was a decision not to initiate an MKI at study entry (Cohort 2). Cohorts were compared descriptively. RESULTS: The full analysis set (FAS) comprised 647 patients from 19 countries. The median duration of observation was 35.5 months (range