Correlative analysis of FLT3L levels, P-FLT3 levels, and survival outcome according to FLT3-ITD allelic burden. (A-B) Peripheral blood plasma FLT3L levels assessed on days 4, 10, 15, and 28 after induction in sorafenib (A) and placebo arms (B). (C) P-FLT3 levels at day 10 relative to day 4 with a representative example immunoblot of P-FLT3 changes in a PIA responder and nonresponder. Patients with a PIA response but without a clinical response are noted with an asterisk (∗). (D-E) Kaplan-Meier estimate of OS in the sorafenib or placebo arms among patients with FLT3-ITD allelic ratio ≥0.7 (D) or <0.7. D, day (E).