Association of Chromosome Arm 9p Abnormalities With Adverse Risk in Childhood Acute Lymphoblastic Leukemia: A Report From the Children's Cancer Group

Cytogenetic abnormalities of chromosome arm 9p occur frequently in children with acute lymphoblastic leukemia (ALL). We analyzed 201 such cases (11%) in 1,839 children with newly diagnosed ALL treated between 1989 and 1995 on risk-adjusted protocols of the Children's Cancer Group (CCG). The majority of patients (131; 65%) with a 9p abnormality were classified as higher risk. Nearly all patients had complex karyotypes; most cases had deletions of 9p, add/der(9p), a dicentric involving chromosome arm 9p, and/or balanced translocations and inversions involving 9p. Event-free survival (EFS) estimates at 6 years for patients with and without a 9p aberration were 61% (standard deviation [SD] = 5%) and 76% (SD = 2%;P < .0001). In addition, patients with a 9p abnormality had an increased cumulative incidence of both marrow (P = .04) and central nervous system (P = .0001) relapses. Overall survival also was significantly worse for patients with an abnormal 9p (P < .0001). These effects were most pronounced in standard-risk patients (age 1 to 9 years with white blood cell count