Survival Predictors of Radioiodine-refractory Differentiated Thyroid Cancer Treated With Lenvatinib in Real Life

Context: Lenvatinib is approved for the treatment of radioiodine-refractory differentiated thyroid cancer (RR-DTC). The definition of predictive factors of survival is incomplete. Objective: To identify pre- and posttreatment survival predictors in a real-life cohort of RR-DTC treated with lenvatinib. Design: Multicenter, retrospective, cohort study. Setting: 3 Italian thyroid cancer referral centers. Participants: 55 RR-DTC treated with lenvatinib. Main Outcome Measures: Progression-free survival (PFS) and overall survival (OS). Results: Lenvatinib was the first-line kinase-inhibitor in 96.4% of subjects. Median follow-up was 48 months. Median PFS and OS were 26 [95% confidence interval (CI) 19.06-32.93] and 70 months (95% CI 36-111.99), respectively. Pretreatment setting: Eastern Cooperative Oncology Group (ECOG) performance status was independently related to PFS [P < .001; hazard ratio (HR) 18.82; 95% CI 3.65-97.08: score 0-1 as reference] and OS (P = .001; HR 6.20; 95% CI 2.11-18.20; score 0-1 as reference); radioactive iodine (RAI) avidity was independently related to PFS (P = .047; HR 3.74; 95% CI 1.01-13.76; avid disease as reference). Patients with good ECOG status (0-1) and RAI-avid disease obtained objective response in 100% of cases and achieved a median PFS of 45 months without any death upon a median follow-up of 81 months. Posttreatment setting: the best radiological response independently predicted PFS (P = .001; HR 4.6; 95% CI 1.89-11.18; partial/complete response as reference) and OS (P = .013; HR 2.94; 95% CI 1.25-6.89; partial/complete response as reference). Conclusion: RR-DTC with good performance status and RAI-avid disease obtains the highest clinical benefit from lenvatinib. After treatment initiation, objective response was the only independent survival predictor.