Deletion analysis of p16(INKa) and p15(INKb) in relapsed childhood acute lymphoblastic leukemia.

This study aimed at determining the prevalence of INK4 deletions and their impact on outcome in 125 children with acute lymphoblastic leukemia (ALL) at first relapse using real-time quantitative polymerase chain reaction. Patients were enrolled into relapse trials ALL-REZ BFM (ALL-Relapse Berlin-Frankfurt-Münster) 90 and 96. The prevalence of p16(INK4a) and p15(INK4b) homozygous deletions was 35% (44 of 125) and 30% (38 of 125), respectively. A highly significant association of both gene deletions was found with the 2 major adverse prognostic factors known for relapsed childhood ALL: T-cell immunophenotype and first remission duration. There was no correlation between INK4 deletions and probability of event-free survival. These findings argue against an independent prognostic role of INK4 deletions in relapsed childhood ALL.