Clinical relevance of T-cell receptor delta gene rearrangements in childhood B-precursor cell acute lymphoblastic leukaemia.

The large majority of childhood B-precursor cell acute lymphoblastic leukaemia cases present IgH and TCRdelta gene rearrangements. These rearrangements have been widely used as specific markers for monitoring minimal residual disease. However, their prognostic value still remains unclear. In order to determine whether IgH and TCRdelta gene rearrangements have any influence on relapse and event-free survival (EFS), we analysed the clinical impact of these genetic characteristics in 51 B-precursor acute lymphoblastic leukaemia patients. 46/51 patients (90.2%) showed IgH gene rearrangements by Southern blot and/or polymerase chain reaction (PCR) analysis. No statistically significant associations were found between IgH gene rearrangement pattern and age, sex, WBC count, immunophenotype, risk factor, relapse or EFS. 27/41 patients (66%) showed Vdelta2Ddelta3 recombination by Southern blot and/or PCR analysis. At a median follow-up of 53 months the estimated 5-year EFS probability was 78 +/- 3% for the whole group. The EFS probability among patients with a Vdelta2Ddelta3 recombination pattern in the TCRdelta locus was 90 +/- 3%, whereas for patients without Vdelta2Ddelta3 recombination was 39 +/- 13% (P < 0.005). IgH rearrangement patterns do not appear to influence relapse or EFS probability. However, TCRdelta gene rearrangement patterns have a relevant impact on the relapse rate and the EFS probability. Patients with Vdelta2Ddelta3 recombination have better clinical outcome than patients without this recombination, independent of any other prognostic factors.