FLT3 and acute myeloid leukemia: The R/R AML patients (n = 29) had significantly higher ITD-AR (P = 0.024; median: 0.39; 95% CI 0.302–0.478) compared to unmatched diagnostic samples (n = 22) (median: 0.27; 95% CI 0.164–0.369), which indicates that cellular addiction on activated FLT3-signaling increases during disease progression.