A hypodiploid karyotype in childhood B-cell precursor acute lymphoblastic leukemia

Abstract

The detection of genetic markers associated with poor prognosis is crucial to the selection of an appropriate treatment plan for B-cell precursor acute lymphoblastic leukemia (BCP-ALL). A hypodiploid karyotype in patients with BCP-ALL has an unfavorable impact and serves as a criterion for the stratification of patients into a high-risk group. However, the survival rates of patients with a hypodiploid karyotype remain poor. Russian treatment protocols for childhood acute lymphoblastic leukemia do not include a hypodiploid karyotype in risk stratification criteria. In order to determine the prognostic value of a hypodiploid karyotype and the clinical characteristics of BCP-ALL in patients with a hypodiploid karyotype, we analyzed the survival rates of 2,700 patients included in a multicenter study. Our study was approved by the Independent Ethics Committee and the Scientific Council of the D. Rogachev NMRCPHOI of the Ministry of Healthcare of the Russian Federation. All patients underwent karyotyping and fluorescence in situhybridization (FISH) testing. A hypodiploid karyotype was detected in 27 patients. Eighteen out of 27 patients had a hypoploid clone (according to karyotyping results), 2 patients had a doubled near-haploid clone (according to karyotyping and FISH results); in 7 patients with a normal karyotype or in the absence of mitosis, hypodiploidy was determined only by FISH test. BCP-ALL with hypodiploidy is usually associated with increased WBC count at disease onset. The median WBC count in the study group was 24.2 (3.4–206.0) × 109/l vs 10.3 (0.2–1290.0) × 109/l in the control group. The number of patients with initial leukocytosis < 30 × 109/l in the study group was significantly lower than in the control group (p< 0.062). Remission was achieved in 26/27 patients. The event-free survival rates in patients with hypodiploidy were significantly lower than in those without hypodiploidy: 50 ± 11% vs 72 ± 8% (p< 0.0001). The overall survival was 64 ± 10% and 90 ± 1%, respectively (p< 0.0001). The cumulative incidence of relapse in patients with a hypodiploid karyotype was higher (42.6 ± 10.9%) than in the controls (22.3 ± 8.1%) (p< 0.0001). The patients who received more intense treatment for intermediate- and high-risk groups showed better survival rates than those in the standard-risk group: 62 ± 13% vs 40 ± 15% (р= 0.59); the cumulative incidence of relapse according to the risk group was 26.4 ± 12.1% and 60 ± 16.9%, respectively (р= 0.19).The highest risk of relapse was observed in a group that included patients with near-haploidy and low hypodiploidy (26–39 chromosomes; 52.9 ± 14.4%). The event-free survival in this group was 36 ± 13%. The results of treatment of patients with BCP-ALL and hypodiploidy according to the national guidelines turned out to be comparable to the international ones. Patients with BCP-ALL and hypodiploidy should be initially stratified to the most intense treatment arm. In order to identify patients with hypoploidy, standard karyotyping is required; where needed, it can be supplemented by FISH analysis