Hyperdiploidy with 58-66 chromosomes in childhood B-acute lymphoblastic leukemia is highly curable: 58951 CLG-EORTC results

The aim of our study was to analyze the factors contributing to heterogeneity of prognosis in patients with hyperdiploidy>50 chromosomes (HD>50), a group of B-cell precursor acute lymphoblastic leukemia with favorable outcome. The 541 HD>50 patients registered prospectively in the 58951 CLG-EORTC trial, identified by karyotype (446 patients) and by DNA index (DI) (490 patients), had a 6-year EFS of 89.0% (SE=1.5%) and a 6-year overall survival (OS) of 95.9% (SE=0.9%). The strongest prognostic factor was the modal number of chromosomes (MNC): the 6-year EFS of 51-53, 54-57 and 58-66 MNC groups were 80%, 89% and 99% respectively (P1.16- 1.24 were 83%, 90% and 95% respectively (P=0.009). All usual combinations of trisomies (chromosomes 4,10,17,18) were significant favorable factors but had lower EFS when MNC was lower than 58. In multivariate analysis, MNC remained the strongest factor. Consequently, the best indicator for excellent outcome was ploidy assessed by karyotype because patients with 58-66 chromosomes stood every chance of being cured (OS of 100% at 6-year follow-up) with less intensive therapy.

Trefwoorden:B-ALL, hyperdiploidy