Influence of tumor size and Eastern Cooperative Oncology Group performance status (ECOG PS) at baseline on patient (pt) outcomes in lenvatinib-treated radioiodine-refractory differentiated thyroid cancer (RR-DTC).

Abstract

6081 Background: In SELECT, lenvatinib significantly improved progression-free survival (PFS) of pts with RR-DTC versus placebo (18.3 v 3.6 months; hazard ratio [HR]: 0.21 [99% CI: 0.14, 0.31]; P<0.001). Here we examine the treatment of RR-DTC with lenvatinib in relation to tumor size (sum of all targeted lesions) and ECOG PS. Methods: In this post hoc analysis of SELECT with pts randomized to receive lenvatinib, Kaplan-Meier estimates of time to ECOG PS ≥2 were calculated for subgroups of pts according to baseline ECOG PS or tumor size. Objective response rate (ORR) and Kaplan-Meier estimates of overall survival (OS) and PFS according to ECOG PS (0 or 1) at baseline were calculated. Correlations between ECOG PS at baseline (0 or 1) and maximum tumor shrinkage were calculated using one-way analysis of variance. Results: Pts with ECOG PS 0 or 1 at baseline had similar demographic and disease characteristics. ORR was 78.5% and 51.0% for pts with ECOG PS 0 and 1 at baseline, respectively (odds ratio [95% CI]: 3.508 [2.018, 6.097]). Mean maximum percent decrease in tumor size was significantly greater in pts with baseline ECOG PS 0 (-46.13%) versus pts with ECOG PS 1 (-37.16%; P=0.0017). For pts with ECOG PS 1 at baseline, time to ECOG PS ≥2 was numerically shorter with tumor size >60 mm versus tumor size ≤60 mm (HR [95% CI]: 1.450 [0.708, 2.967]). Additional results are summarized in the table. Conclusions: Among pts with RR-DTC, PFS, OS, ORR, and time to ECOG ≥2 were generally better for patients with lower ECOG PS or smaller tumor size at baseline. These results may indicate that it is beneficial to start lenvatinib in pts with RR-DTC early, before ECOG PS worsens and tumor size increases. Clinical trial information: NCT01321554. [Table: see text]