Postinduction minimal residual disease monitoring by polymerase chain reaction in children with acute lymphoblastic leukemia

Purpose: Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer. Monitoring minima residual disease (MRD) by using real-time quantitative polymerase chain reaction (RQ-PCR) provides information for patient stratification and individual risk-directed treatment. Cooperative studies have documented that measurement of blast clearance from the bone marrow during and after induction therapy identifies patient populations with different risk of relapse. We explored the possible contribution of measurements of MRD during the course of treatment.Patients and Methods: We used RQ-PCR to detect MRD in 110 unselected patients treated in Italy in the International Collaborative Treatment Protocol for Children and Adolescents With Acute Lymphoblastic Leukemia (AIEOP-BFM ALL 2000). The trial took place in AIEOP centers during postinduction chemotherapy. Results were categorized as negative, low positive (below the quantitative range [< 5 × 10-4]), or high positive (≥ 5 × 10-4). Patients with at least one low-positive or high-positive result were assigned to the corresponding subgroup.Results: Patients who tested high positive, low positive, or negative had significantly different cumulative ncidences of leukemia relapse: 83. 3%, 34. 8%, and 8. 6%, respectively (P <. 001). Two thirds of positive cases were identified within 4 months after induction-consolidation therapy, suggesting that this time frame may be most suitable for cost-effective MRD monitoring, particularly in patients who did not clear their disease at the end of consolidation.Conclusion: These findings provide further insights into the dynamic of MRD and the ongoing effort to define molecular relapse in childhood ALL