Outcome of allogeneic hematopoietic stem cell transplantation for cytogenetically normal AML and identification of high-risk subgroup using WT1 expression in association with NPM1 and FLT3-ITD mutations

According to recent guidelines, cytogenetically normal acute myeloid leukemia (CN AML) is divided into four molecular subgroups based on nucleophosmin-1 (NPM1) and FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) mutations. All subgroups except for isolated NPM1mut are associated with poor prognosis. We retrospectively analyzed 223 patients with CN AML, 156 of whom were treated with standard chemotherapy. For postremission therapy, patients with available donors underwent allogeneic (allo) hematopoietic stem cell transplantation (HSCT) and the rest were treated with autologous HSCT or chemotherapy alone. We first compared the 4 conventional molecular subgroups, and then created another 4 subgroups based on WT1 expression: isolated NPM1mut, NPM1wt/FLT3-ITD-neg with low WT1 or high WT1, and FLT3-ITD-pos CN AML. We finally evaluated 89 patients who were treated with allo HSCT and achieved complete remission after standard chemotherapy. FLT3-ITD CN AML showed the worst outcome irrespective of NPM1mut, and isolated NPM1mut CN AML showed no significant differences compared with NPM1wt/FLT3-ITD-neg CN AML. In contrast, two newly stratified low-risk subgroups (NPM1wt/FLT3-ITD-neg with low WT1 and isolated NPM1mut CN AML) showed higher remission rates with superior overall survival (OS) compared with the other two high-risk subgroups, which showed a higher relapse rate even after allo HSCT. Further analysis showed that higher pre-HSCT expression of WT1 resulted in a higher relapse rate and poorer OS after allo HSCT. For CN AML, a risk-adapted approach using allo HSCT with novel agents should be evaluated with stratification specified by WT1.