Assessment of Minimal Residual Disease by Flow Cytometry in Acute Myeloid Leukaemia and its Correlation with Treatment Outcome

Background: Acute myeloid leukaemia is the most common acute leukaemia in adults with increasing incidence, and despite major advances relapse is still a major concern. Assessing the response to therapy by determination of blast morphology is not sufficient to predict relapse in AML patients. Given its applicability to the majority of patients, FCM provides a powerful, independent prognostic factor to individualize therapy in AML patients.Materials and methods: This study was conducted on 50 Egyptian adult AML patients. They were at day 28 post induction/post consolidation. FCM on bone marrow samples using FITC, PE, PC labelled CDs and a panel of antibodies tailored to each patient is used to assess MRD.Results: Using a cut off value of 0.01% to assess MRD, 32% of patients had negative MRD and 68% had a positive MRD. In 58% of patients, lineage infidelity was used, CD19 was the most common marker used in 62% of patients while CD7 was used in 31% and CD56 was used in 7%. 73% of cases with positive MRD had apparently normal initial cytogenetics while 62% of negative MRD cases had t (8; 21). Collectively, 100% of MRD-ve cases are still in remission after 6 months of therapy while 61.8% of cases with positive MRD relapsed. MRD was in the lower range in cases with remission (0.545) and a higher range (0.44) in relapsed cases.Conclusion: Our results indicate that measurement of MRD after induction/consolidation therapy provides a powerful prognostic factor for outcome in patients with AML.