Clinical Significance of FLT3 Internal Tandem Duplication in Patients with Acute Myeloid Leukemia Who Underwent Allogeneic Bone Marrow Transplantation.

Since the introduction of high-dose cytarabine therapy, there are still controversies for the role of allogeneic or autologous stem cell transplantation (SCT) in acute myeloid leukemia (AML), but the SCT, especially allogeneic, has a benefit in AML patients with intermediate risk. However, it is needed to investigate for a new prognostic factor, in addition to the cytogenetics, to the further stratifying approach. Internal tandem duplications (ITD) within FLT3 are present in 20–30% of patients with AML and have a prognostic implication in the disease. However, there was no report in AML patients who underwent allogeneic bone marrow transplantation (BMT). In this study, we evaluated the prognostic relevance of FLT3/ITD in 42 patients with AML who underwent allogeneic BMT. FLT3/ITD mutations were studied on bone marrow samples at diagnosis using PCR. As a baseline study, we firstly analyzed the incidence of FLT3/ITD in BM samples at diagnosis of 214 patients with AML. Of the patients, FLT3/ITD were found in 68 patients (31.8%). In this study, 64% of the patients who underwent allogeneic BMT were positive for FLT3/ITD mutations. Methologically, FLT3/ITD detections by melting curve analysis showed higher sensitivity (66.7%) than those by gel electrophoresis (61.9%). There were no significant differences in the engraft periods and the incidence of acute and chronic GVHD according to the presence of FLT3/ITD mutations. When we analyze patient’s survival according to the presence or absence of FLT3/ITD, the probability of overall survival (OS) at 3 years in the AML patients with FLT3/ITD tended to be shorter than those lacking FL3/ITD (53.9 ± 9.9% vs. 60.6 ± 14.7%, P=0.46). In addition, the probability of disease free survival (DFS) at 3 years in the AML patients with and without FLT3/ITD was 57.3±10.3% and 85.7±13.2%, respectively (P=0.046). Among the cytogenetic risk group, low-risk and high-risk groups were no significant differences according to FLT3/ITD despite of the limited number of patients studied. However, patients with intermediate-risk were significantly shorter DFS in the presence of FLT3/ITD than those in the absence of FLT3/ITD (P=0.048). These findings suggest that the presence of FLT3/ITD mutations is a poor prognostic factor for disease free survival in AML patients, especially with cytogenetically intermediate-risk, who underwent allogeneic BMT and melting curve analysis to detect the presence of FLT3/ITD mutations is a useful tool with high sensitivity.