Clinical significance of deletions of chromosome arm 6q in childhood acutelymphoblastic leukemia: A report from the Children's Cancer Group

We have compared outcome for 167 (9.0%) children with a del(6q) and 1713 (9 1%) children without a der(6q) treated on Children's Cancer Group (CCG) ris k-adjusted treatment protocols for acute lymphoblastic leukemia (ALL), Thir ty-three patients had a del(6q) as the sole aberration; 22 patients had a d el(6q) only as a secondary abnormality. Thirty-six cases had a del(6q) and high hyperdiploidy (>50 chromosomes). Six patients with a del(6q) also had +16 and 8 patients had loss of a sex chromosome. Frequent recurring breakpo ints were q13, q15, q21, q23, and q25. Patients with a del(6q) were more li kely to have T-lineage ALL (p < 0.001), a mediastinal mass (p = 0.01), and higher WBC counts (p = 0.04), although only half of these patients were cla ssified as poor risk. Event-free survival at 6 years was similar for patien ts with or without a del(bq), with estimates of 77% (SD = 5%) and 74% (SD = 2%), respectively (p = 0.44). This finding was also observed within NCI po or and standard risk groups. Thus, cytogenetically detectable del(6q) is no t associated with adverse risk in pediatric ALL.