Serial serum Flt3L measurements in AML patients. (A) Patients were sampled at diagnosis and following each of 2 cycles of intensive chemotherapy with daunorubicin and cytarabine (3+10) or fludarabine, cytarabine, and idarubicin (cohort A, Newcastle; shaded regions indicate normal range). Patients who entered continuing morphological CR after 2 courses maintained increasing Flt3L at remission assessments performed 28 to 42 days after the start of chemotherapy (range of detection, 7-1000 pg/mL; n = 15; broken lines). (B) Patients who did not achieve morphological CR after the first course of chemotherapy but subsequently entered remission after the second also demonstrated increasing Flt3L over both cycles (n = 5; filled circles and solid lines). (C) Patients who remained refractory after 2 courses of chemotherapy had undetectable Flt3L (n = 5; open circles and solid lines). The graph also includes a further 3 patients thought to be in morphological CR after the first course of chemotherapy who experienced relapse within 6 months.