OBJECTIVETo identify ikaros family zinc finger1 (IKZF1) deletion in patients with pediatric B cells-acute lymphoblastic leukemia (B-ALL) without reproducible chromosomal abnomalities and further investigate its value in this part of patients' pathogenesis and prognosis.

METHODThe study was approved by the institutional review board of the authors' hospital and informed consent was obtained from the patients and/or their legal guardians. Data of 96 children with B-ALL patients without reproducible cytogenetic abnormalities whose bone marrows specimens were enough for DNA extraction for the detection were retrospectively selected. All the patients were diagnosed and systematically treated according to CCLG-ALL2008 in our hospital from April 2008 to April 2013. The 96 patients were divided into two groups according to the result of IKZF1's detection by multiplex ligation-dependent probe amplification (MLPA): The cases that with any of eight exons of IKZF1 deleted were entered into"Group with IKZF1 deletion"otherwise entered"Group without IKZF1 deletion". Disease free survival (DFS), event-free survival (EFS) and overall survival (OS) were compared between the two groups.

RESULTNineteen out of 96 B-ALL patients without reproducible cytogenetic abnormalities had IKZF1 deletion (20%). Three of 19 patients with IKZF1 deletions of the whole gene; ten of 19 patients with IKZF1 deletions of exon 1; 4 of 19 patients with IKZF1 deletions of exons 4-7; one of 19 patients with IKZF1 deletions of exons 2-7 and one of 19 patients with IKZF1 deletions of exons 1-6. Whose white blood cell (WBC) ≥ 50 × 10(9)/L inIKZF1 diletion group was more than whthout IKZF1 deletion group(42% vs. 13%, P=0.004). Patients with IKZF1 deletions had a lower 3-year DFS (0.67 ± 0.13 vs. 0.93 ± 0.04, P=0.001); EFS (0.67 ± 0.13 vs. 0.90 ± 0.04, P = 0.012) and OS(0.79 ± 0.09 vs. 0.96 ± 0.02, P=0.010) compared to those without IKZF1 deletions. Excluding the influence of sex, age, WBC count at diagnosis, cerebrospinal fluid state and prednisone response IKZF1 deletion still affected the patients' DFS, EFS and OS ( P<0.05 for all comparisons).

CONCLUSIONSome of pediatric B-cell precursor ALL without reproducible cytogenetic abnormalities had been detected to have IKZF1 deletion; IKZF1 deletion is an independent poor prognostic factor in these patients.