Real-World Outcomes of FLAG-Ida Regimen in 1079 Adult Patients With First Relapsed/Refractory AML: A PETHEMA Study

In a large multicenter real-world cohort, we aimed to evaluate outcomes of FLAG-Ida salvage therapy for relapsed/refractory (R/R) acute myeloid leukemia (AML) and validated the SALFLAGE prognostic score. We analyzed 1079 adults with R/R AML treated across 112 PETHEMA institutions over 26 years (1998-2024), including patients with primary refractory disease (36.9%) and first relapse episode (63.1%), with a median age of 52 years. Complete remission composite (CRc) was achieved 56.8%, including complete remission (CR) in 51.0%, CR with incomplete recovery in 4.0%, and morphological-free-state in 1.8%, enabling 35.2% of patients and 62% of responders to proceed to allogeneic transplantation without morphological disease. With median follow-up of 50.9 months, median overall survival (OS) was 10.2 months, with 5-year OS rate of 21.6%. Prior allogeneic transplantation (HR 0.54; p < 0.001) and relapse-free interval ≥ 1 year (HR 0.75; p = 0.024) independently predicted improved OS, whereas modified high-risk cytogenetics including t(8; 21) (HR 3.58; p < 0.001), FLT3-ITD mutation at primary diagnosis (HR 1.61; p < 0.001), and age ≥ 60 (HR 1.43; p < 0.001) conferred inferior OS. Validation of the SALFLAGE score demonstrated moderate discrimination (C-index 0.67), with 5-year survival of 38.4%, 27.2%, and 12.7% across risk categories (p < 0.001). Outcomes improved over periods (1998-2005 vs. 2006-2016 vs. 2017-2024): 30-day mortality was 6.9% vs. 9.3% vs. 5.0%, respectively (p = 0.030), and median OS was 7.8 versus 9.4 versus 11.1 months, respectively (p = 0.16). We confirm FLAG-Ida as a reference salvage regimen in fit R/R AML and validate the SALFLAGE score in this setting.