Association between Flt3L and post–course 1 remission and survival. Serum Flt3L was measured on day 26 of induction in non-APL AML patients with Flt3 mutation randomized to lestaurtinib (days 11-24) on the UK NCRI AML17 trial. (A) Serum Flt3L at day 26 in patients who subsequently achieved or did not achieve CR. Dotted line indicates optimal cut point identified by the ROC curve: 116 pg/mL (Mann-Whitney UP value). (B) EFS of subgroups with serum Flt3L level ≥291 pg/mL (blue line) or <291 pg/mL (red line). Events include failure to achieve CR and relapse or death from any cause. Threshold of Flt3L for maximum discrimination identified by log-rank testing (log-rank P value). (C) OS of subgroups with a serum Flt3L level ≥1185 pg/mL (blue line) or <1185 pg/mL (red line). Threshold of Flt3L for maximum discrimination identified by log-rank testing (log-rank P value). (D) EFS of subgroups divided according to Flt3L level ≥291 pg/mL and MRD negative (green line, n = 17), ≥291 pg/mL and MRD positive (blue line, n = 15), Flt3L <291 pg/mL and MRD negative (black line, n = 23), or <291 pg/mL and MRD positive (red line, n = 46) (log-rank P value). (E) OS of subgroups divided according to Flt3L level ≥1185 pg/mL and MRD negative (green line, n = 10), ≥1185 pg/mL and MRD positive (blue line, n = 5), Flt3L <1185 pg/mL and MRD negative (black line, n = 30), or <1185 pg/mL and MRD positive (red line, n = 56) (log-rank P value).