Prognostic significance of cytogenetic abnormalities of chromosome arm 12pin childhood acute lymphoblastic leukemia - A report from the Children's Cancer Group

BACKGROUND. The authors have determined the prognostic significance of cyto genetically detectable 12p abnormalities, which are frequent in children wi th acute lymphoblastic leukemia (ALL], in a large cohort of patients treate d on risk-adjusted protocols of the Children's Cancer Group (CCG). METHODS. The presence of an abnormal 12p was identified among 1880 children with newly diagnosed ALL; outcome was assessed by standard Life table meth ods. RESULTS. A total of 174 cases (9%) had cytogenetically detectable 12p abnor malities; the majority of cases had a balanced translocation, a del(12p), o r an add(12p). In the overall cohort, event free survival (EFS) at 6 years was similar for patients with or without a 12p abnormality (76%, SD = 6%, v s. 75%, SD = 2%, respectively; P = 0.60). Among patients with pseudodiploid y, an abnormal 12p conferred improved outcome (P = 0.008; relative risk = 0 .51; 95% confidence interval [CI], 0.31-0.85). There was a trend for improv ed EFS for those with abnormalities in both chromosome 12 homologues (P = 0 .16; relative risk = 0.39; 95% CI, 0.10-1.55) and those with low hyperdiplo idy (P = 0.07; relative risk = 0.44; 95% CI, 0.18 -1.09]. Among T-lineage A LL patients, there was a trend for worse outcome for abnormal versus normal 12p (P = 0.14; relative risk = 1.97; 95% CI, 0.78-4.93]. There was no diff erence in EFS for the 12 patients with a dic(9;12) compared with patients l acking an abnormal 12p. CONCLUSIONS. These data suggest that although a cytogenetically detectable 12p aberration is a favorable risk factor for children with. ALL and pseudo diploidy, it is not prognostic for the overall group of pediatric ALL patie nts treated with contemporary therapies of the CCG. Cancer 2000;88:1945-54. (C) 2000 American Cancer Society.