OBJECTIVETo assess the prognostic value of minimal residual disease (MRD) in childhood B-cell acute lymphoblastic leukemia (ALL) after induction chemotherapy.

METHODSFrom September 2001 to October 2004, 102 patients with newly diagnosed B-ALL were enrolled in protocol ALL-XH-99. MRD after induction therapy, before high-dose methotrexate and early intensification as well as at 1 year and 2 year maintenance therapy was detected by multiparameter-flow-cytometry (MP-FCM).

RESULTS(1) The probability of 39-month event-free survival (EFS) for patients with a level of MRD < 10(-4), was significantly higher than for those with a higher MRD [(83.00 +/- 9.90)% vs 0.00%, P < 0.01]. (2) Univariate analysis indicated that the MRD level at achieving complete remission (CR) had no relationship with the biologic features at presentation (gender, age, white blood cells and cytogenetic abnormalities), but did with Philadelphia chromosome, the time reaching CR, ALL-XH-99 risk group and lymphoblasts in bone marrow on day 19 after induction therapy (P < 0.05). (3) Multivariate analysis suggested that MRD level after the first induction course was an independent prognostic factor (hazard ratio, 5.381; 95% CI 0.004 to 0.624; P < 0.05).

CONCLUSIONThe MRD level at achieving CR is one of important prognostic factor in the treatment of childhood B-cell ALL, and might be used to assess the early treatment response.