Flow Cytometry based 'Acute Myeloid Leukemia Maturity Score' is a Novel Marker for Predicting Relapse in Acute Myeloid Leukemia: A Prospective Observational Study

Objectives:  A novel flow cytometric ‘AML Maturity Score (AMS)’ classifying patients into AML-immature (AML-im) and AML-mature (AML-ma) based on CD34, CD117 and Tdt expression on blasts correlated with induction remission, relapse free survival and overall survival in previous studies. We aimed to study the correlation between AMS and ELN risk group and outcomes- induction remission (IR), time to remission (TTR) and relapse. Material and Methods:  This was a combined prospective and retrospective study of 104 AML patients over 30 months. Flow cytometry based quantitative expression of CD34, TdT and CD117 on blasts was used for calculating AMS and additional tube for CD34+CD38-CD123+ cells was put at diagnosis in 47 patients prospectively studied. The patients received 1-2 cycles of standard induction (3+7) comprising Daunorubicin (60mg/m2/day for 3 days) and Cytarabine (continuous infusion 100mg/m2/day for 7 days). Data was collected on the clinical and laboratory parameters, cytogenetics and molecular profile of these patients who were followed up for IR, TTR and relapse. Results: Of 104 patients, AML-im were 86.6% (90/104) and AML-ma were 13.4% (14/104). Patients were classified as – favorable risk (28.8%), intermediate risk (50%) and adverse risk (21.1%) on the basis of ELN 2017. Of 104 patients, 74 attained IR and of 65 patients followed up over mean period of 18 months, 27 relapsed. The mean AMS was significantly more in patients who attained IR (p=0.003). On classifying patients as AML-im and AML-ma, TTR (p=0.000) and relapses (p=0.043) were significantly higher in AML-im group. Conclusion:  AMS is a novel flow cytometry based potential marker for predicting relapses in AML patients.