Clinical Significance of Minimal Residual Disease at the End of Remission Induction Therapy in Childhood Acute Lymphoblastic Leukemia

BACKGROUND: Detection of minimal residual disease (MRD) in the early phase of therapy is the most powerful predictor of relapse risk in children with acute lymphoblastic leukaemia (ALL). AIM: We aimed to determine the significance of MRD at the end of remission induction therapy in the prediction of treatment outcome in children with ALL. METHODS: Sixty-four consecutive patients aged 1-14 years with newly diagnosed ALL were enrolled in this study from January 2010 to October 2017. All patients were treated according to the ALL IC BFM 2002 protocol. MRD was detected at the end of remission induction therapy (day 33) by multiparameter 6-colour flow cytometry performed on bone marrow specimens with a sensitivity of 0.01%. RESULTS: Overall, 42.2% of patients had detectable MRD on day 33 of therapy. MRD measurements were not significantly related to presenting characteristics but were associated with a poorer blast clearance on day 8 and 15 of remission induction therapy. Patients with negative MRD status on day 33 had a 5-year event-free survival of 94.6% compared with 76.1% for those with positive MRD status (P = 0.044). CONCLUSION: MRD levels at the end of remission induction therapy measured by multiparameter flow cytometry have clinical significance in childhood ALL. High levels of MRD are strongly related to poor treatment outcome.