High fms-like tyrosine kinase-3 (FLT3) receptor surface expression predicts poor outcome in FLT3 internal tandem duplication (ITD) negative patients in adult acute myeloid leukaemia: a prospective pilot study from India

BACKGROUND & OBJECTIVES: Mutations in fms-like tyrosine kinase 3 (FLT3) receptor have significant role in assessing outcome in patients with acute myeloid leukaemia (AML). Data for FLT3 surface expression in relation to FLT3 internal tandem duplication (ITD) status and outcome are not available from India. The objective of the current study was to investigate adult patients with AML for FLT3 expression and FLT3 ITD mutation, and their association with long-term outcome. METHODS: Total 51 consecutive de novo AML patients aged 18-60 yr were enrolled in the study. FLT3 ITD was detected by polymerase chain reaction (PCR); flowcytometry and qPCR (Taqman probe chemistry) were used for assessment of FLT3 protein and transcript, respectively. Kaplan Meier curves were obtained for survival analysis followed by log rank test. RESULTS: FLT3 ITD was present in eight (16%) patients. Complete remission was achieved in 33 (64.6%) patients. At 57.3 months, event free survival (EFS) was 26.9±6.3 per cent, disease free survival (DFS) 52.0±9.2 per cent, and overall survival event (OS) 34.5±7.4 per cent. FLT3 surface expression was positive (>20%) by flow-cytometry in 38 (88%) of the 51 patients. FLT3 surface expression and transcripts were not associated with FLT3 ITD status. FLT3 expression was significantly associated with inferior EFS (P=0.026) and OS (P=0.018) in those who were negative for FLT3 ITD. INTERPRETATION & CONCLUSIONS: This study evaluated FLT3 ITD mutation along with FLT3 expression in AML patients, and associated with survival. Negative impact of FLT3 surface expression on survival was observed in AML patients who were FLT3 ITD negative.