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 ris k. Nearly all patients had complex karyotypes; most cases had deletions of 9p, add/der(gp), a dicentric involving chromosome arm 9p, and/or balanced t ranslocations and inversions involving 9p. Event-free survival (EFS) estima tes at 6 years for patients with and without a 9p aberration were 61% (stan dard deviation [SD] = 5%) and 76% (SD = 2%; P < .0001). In addition, patien ts with a 9p abnormality had an increased cumulative incidence of both marr ow (P = .04) and central nervous system (P = .0001) relapses. Overall survi val also was significantly worse for patients with an abnormal 9p (P < .000 1). These effects were most pronounced in standard-risk patients (age 1 to 9 years with white blood cell count <50,000/mu L): 6-year EFS of 61% (SD = 9%) versus 80% (SD = 2%; P < .0001). Also, a 9p aberration was an adverse r isk factor for B-lineage, but not T-lineage patients. The effect of 9p stat us on EFS was attenuated, but maintained in a multivariate analysis of EFS after adjustment for Philadelphia chromosome status, age, white blood cell (WBC) count, sex, race, and ploidy group (P = .01). Thus, abnormalities of chromosome arm 9p identify a subgroup of standard-risk patients with increa sed risk of treatment failure. (C) 1999 by The American Society of Hematolo gy.