Detection of minimal residual disease in childhood acute lymphoblastic leukemia after termination of therapy

Using IgH and TCR(gamma) gene rearrangements as gene markers, we detected minimal residual disease (MRD) by means of the polymerase chain reaction (PCR) and restriction analysis. Of 18 children with acute lymphoblastic leukemia (ALL), MRDs were detected in 9 patients after termination of therapy. All 18 patients had been followed for 1.5 to 102 months after detection. Three of the nine MRD-positive patients relapsed within 3 to 6 months; none of the nine MRD-negative patients relapsed. We suggest that MRD negativity at th end of therapy might be an important factor for long-term disease-free survival, because the negative cases had a very low risk of relapse. Because the outcome for MRD-positive cases is more difficult to evaluate, patients with MRD after termination of therapy should be monitored.