Rearrangement of the MLL Gene Confers a Poor Prognosis in Childhood Acute Lymphoblastic Leukemia, Regardless of Presenting Age

MLL gene rearrangements are associated with an extremely poor prognosis in infants with acute lymphoblastic leukemia (ALL), but little is known about their clinical significance in older children. Therefore, we studied 45 cases of childhood ALL with abnormalities of chromosome 11q23 for rearrangement of the MLL gene to determine if this feature confers a uniformly poor prognosis. MLL gene rearrangements were detected in all 18 cases with the common t(4; 11). t(9; l l ) or t(11;19) translocations, whereas only 5 of 12 patients with either unbalanced or uncommon balanced translocations demonstrated a rearrangement. Abnormalities of the MLL gene were not detected in any of the 15 cases with a deletion or inversion of the chromosome l lq23 region. The presence of an MLL rearrangement was significantly associated with age less than 1 year (P < .001), leukocyte count >50 x lo9/