Impact of cytogenetics on outcomes in pediatric acute lymphoblastic leukemia

In acute lymphoblastic leukemia (ALL), the most important prognostic factors are age, leukocyte count at presentation, immunophenotype, and cytogenetic abnormalities. The cytogenetic abnormalities are associated with distinct immunologic phenotypes of ALL and characteristic outcomes.

The present study was primarily aimed at analyzing the impact of cytogenetics on postinduction responses and event-free survival (EFS) in pediatric patients with ALL. The secondary objective was to study the overall survival (OS).

A total of 240 patients with age <18 years and diagnosed with ALL between January 2011 and June 2016 were retrospectively analyzed. Cytogenetics was evaluated with conventional karyotyping or reverse transcriptase polymerase chain reaction. Based on cytogenetic abnormalities, the patients were grouped into five categories, and the outcomes were analyzed.

Of the 240 patients, 125 (52%) patients had evaluable cytogenetics. Of these, 77 (61.6%) patients had normal cytogenetics, 19 (15.2%) had t(9;22) translocation, 10 (8%) had unfavorable cytogenetics which included t(9;11), hypodiploidy, and complex karyotype, 10 (8%) had favorable cytogenetics which included t(12;21), t(1;19), and high hyperdiploidy, 9 (7.2%) had miscellaneous cytogenetics. Seventy-one percent of patients were treated with MCP 841 protocol, while 29% of patients received BFM-ALL 95 protocol. The 3-year EFS and OS of the entire group were 52% and 58%, respectively. On univariate analysis, EFS and OS were significantly lower in t(9;22) compared to normal cytogenetics (P = 0.033 and P = 0.0253, respectively) and were not significant for other subgroups compared to normal cytogenetics. On multivariate analysis, EFS was significantly lower for t(9;22) and unfavorable subgroups.

Cytogenetics plays an important role in the molecular characterization of ALL defining the prognostic subgroups. Patients with unfavorable cytogenetics and with t(9;22) have poorer outcomes.