Expression of phosphorylated signal transducer and activator of transcription 5 is associated with an increased risk of death in acute myeloid leukemia

Background Constitutive activation of STAT5 (by phosphorylation) has been identified in a number of malignancies, including acute myeloid leukemia (AML). Objectives We investigated whether the level of phosphorylated STAT5 (pSTAT5) expression correlates with clinical outcome in AML. Methods Adult patients with newly diagnosed AML receiving induction chemotherapy and with an available diagnostic bone marrow were evaluated. Results Forty-two percent of patients had pSTAT5 expression >0 on immunohistochemical analysis of fixed bone marrow core biopsies. In multivariable analyses, controlling for age, history of antecedent hematologic disorder, cytogenetic risk, and WBC at diagnosis, pSTAT5 expression was significantly associated with an increased risk of death (HR 1.96, 95% CI 1.193.23, P similar to=similar to 0.008) and of relapse after achieving complete remission (HR 2.31, 95% CI 1.164.63, P similar to=similar to 0.018). Conclusions Validation of pSTAT5's prognostic value requires additional study in a larger group of uniformly treated patients. However, our data suggests that targeting this signaling pathway in AML may improve the outcome of patients.