RESUMO
BACKGROUND: Immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements function as specific markers for minimal residual disease (MRD), which is one of the best predictors of outcome in childhood acute lymphoblastic leukemia (ALL). We recently reported on the prognostic value of MRD during the induction of remission through a simplified PCR method. Here, we report on gene rearrangement frequencies and offer guidelines for the application of the technique. PROCEDURE: Two hundred thirty-three children had DNA extracted from bone marrow. Ig and TCR gene rearrangements were amplified using consensus primers and conventional PCR. PCR products were submitted to homo/heteroduplex analysis. A computer program was designed to define combinations of targets for clonal detection using a minimum set of primers and reactions. RESULTS: At least one clonal marker could be detected in 98% of the patients, and two markers in approximately 80%. The most commonly rearranged genes in precursor B-cell ALL were IgH (75%), TCRD (59%), IgK (55%), and TCRG (54%). The most commonly rearranged genes for T-ALL were TCRG (100%) and TCRD (24%). The sensitivity of primers was limited to the detection of 1 leukemic cell among 100 normal cells. CONCLUSIONS: We propose that eight PCR reactions per ALL subtype would allow for the detection of two markers in most cases. In addition, these reactions are suitable for MRD monitoring, especially when aiming the selection of patients with high MRD levels (≥ 10(-2)) at the end of induction therapy. Such an approach would be very useful in centers with limited financial resources.