IKZF1 (Ikaros) Deletions in BCR-ABL1-Positive Acute Lymphoblastic Leukemia Are Associated With Short Disease-Free Survival and High Rate of Cumulative Incidence of Relapse: A GIMEMA AL WP Report

PURPOSE: The causes of the aggressive nature of BCR-ABL1-positive adult acute lymphoblastic leukemia (ALL) are unknown. To identify, at the submicroscopic level, oncogenic lesions that cooperate with BCR-ABL1 to induce ALL, we performed an investigation of genomic copy number alterations using single nucleotide polymorphism array, genomic polymerase chain reaction, and sequencing of candidate genes. PATIENTS AND METHODS: Eighty-three patients with de novo adult Philadelphia chromosome (Ph) -positive ALL were enrolled onto institutional (n = 17) or Gruppo Italiano Malattie Ematologiche Maligne dell'Adulto Working Party delle Leucemia Acute (n = 66) clinical trials. Treatments included tyrosine kinase inhibitor (TKI) alone, conventional chemotherapy, or a combination of TKI and chemotherapy. RESULTS: A 7p12 deletion of IKZF1 (Ikaros) was identified in 52 (63%) of 83 patients. The pattern of deletion varied among different patients, but the two most common deletion types were loss of exons 4 to 7 in 31 (37%) of 83 patients and loss of exons 2 to 7 in 17 (20%) of 83 patients. Disease-free survival (DFS) was shorter in patients with IKZF1 deletion versus patients with IKZF1 wild type (10 v 32 months, respectively; P = .02). Furthermore, a significantly shorter cumulative incidence of relapse was recorded in patients with IKZF1 deletion versus patients with IKZF1 wild type (10.1 v 56.1 months, respectively; P = .001). Multivariate analysis confirmed the negative prognostic impact of IKZF1 deletion on DFS (P = .04). CONCLUSION: We conclude that IKZF1 deletions are likely to be a genomic alteration that significantly affects the prognosis of Ph-positive ALL in adults.