The FOSSIL Study: FLAG or standard 7+3 induction therapy in secondary acute myeloid leukemia

•FLAG induction produces 70% overall response rates in secondary AML.•Induction mortality rate was 3% and duration of neutropenia was shorter with FLAG.•FLAG induction allowed half of all patients to proceed to consolidation therapy.•FLAG represents a highly effective, lower-cost approach to treating secondary AML. Patients with secondary acute myeloid leukemia (sAML) have poor outcomes, with CR/CRi rates of 25–35% with standard 7 + 3 induction chemotherapy, while single center non-comparative analyses suggest promising outcomes with FLAG. We conducted a single-center, retrospective cohort study assessing outcomes in treatment-naïve patients with sAML treated with fludarabine, high-dose cytarabine, and granulocyte colony-stimulating factor (FLAG, n = 40) compared with 7 + 3 (n = 66). Median patient age was 63 years (range: 27–82) in the FLAG group and 60 years (range: 21–76) in the 7 + 3 group (P = 0.968). Patients treated with FLAG achieved higher overall response rates (CR + CRi + MLFS) compared to 7 + 3 (70% vs. 48%, P = 0.043). FLAG was well tolerated, with only one induction death (30-day mortality rate, 3% vs. 8%, P = 0.405) and no cases of cerebellar toxicity. Duration of neutropenia was significantly shorter with FLAG (median 16 vs. 23 days, P