Allogeneic HSCT at the first remission for younger adults with FLT3-ITD AML: The JALSG AML209-FLT3-SCT Study.

: In this phase II multicenter study (JALSG AML209-FLT3-SCT), we aimed to prospectively elucidate the role of allo-HSCT at CR1 for FLT3-ITD-positive AML. Newly diagnosed de novo AML patients with FLT3-ITD were enrolled at the achievement of CR1 and received allo-HSCT as soon as possible after the first consolidation therapy. Mutations of 57 genes in AML cells at diagnosis were also analyzed. Among 48 eligible patients with a median age of 38.5 (17-49) years, 36 (75%) received allo-HSCT at a median of 108 days after CR1. The median follow-up was 1726 days. The primary endpoint, 3-year disease-free survival (DFS) based on an intent to treat analysis, was 43.8% (95%CI, 30-57%), suggesting the efficacy of this treatment because the lower limit of the 95%CI exceeded the threshold response rate of 20%. The 3-year overall survival, post-transplant DFS, and non-relapse mortality rates were 54.2% (95%CI, 39-67%), 58.3% (95%CI, 41-72%), and 25.0% (95%CI, 12-40%), respectively. The median ITD allelic ratio (AR) was 0.344 (0.006-4.099). Neither FLT3-ITD AR nor co-occurring genetic alterations was associated with a poor DFS. This prospective study demonstrated the efficacy and safety of allo-HSCT for FLT3-ITD AML patients in CR1. This study was registered at www.umin.ac.jp/ctr/ as #UMIN000003433.