Prospective Monitoring and Quantitation of Residual Blasts in Childhood Acute Lymphoblastic Leukemia by Polymerase Chain Reaction Study of 6 and y T-cell Receptor Genes

We have developed a strategy based on polymerase chain reaction (PCR) for detecting all possible y T-cell receptor (yTCR) rearrangements and the most common GTCR re-arrangements found in B-lineage and T-acute lymphoblastic leukemia (T-ALL). The segments amplified from blasts are then directly sequenced to derive clonospecific probes. From a series of 45 patients aged 1 to 15 yean (42 B-lineage ALL, 3 T-ALL), 35 (83%) could be followed for minimal residual disease with at least one clonospecific probe. Detection of clonal markers using clonospecific probes routinely allowed the detection of 1 to 10 blasts out of 10 ’ cells as determined by serial dilutions of the initial samples. Residual disease was quantitated by a competitive PCR assay based on the coampliiication of an internal standard. Twenty children were prospectively followed for periods varying from 7 t