Children With Acute Lymphoblastic Leukemia in Romania: Results From a Decade-Long Single-Center Study

Background: Acute lymphoblastic leukemia (ALL) is the most prevalent cancer in children, with continuously improving survival rates. As few studies in Romania have analyzed ALL patients and disease characteristics or survival, we conducted a retrospective study on 158 patients diagnosed with ALL admitted to the Department of Pediatric Oncology and Hematology at the Emergency Hospital for Children, Cluj-Napoca, Romania, from January 2011 until April 2021. The most important objectives of the study are to establish full profiles of the patients and ALL, remission rates, relapses, and deaths, an epidemiology analysis to determine the incidence of ALL for comparison with the standard European population, and also to assess survival by the most important parameters, including minimal residual disease (MRD).

Methods: This was a retrospective study that focused on patients with newly diagnosed ALL from January 2011 to April 2021 in the Department of Pediatric Hematology and Oncology of the Emergency Hospital for Children, Cluj-Napoca, Romania. The inclusion criteria were: patients with de novo ALL, patients who were younger than 18 years of age, and patients with signed informed consents. The exclusion criteria included patients who were older than 18 years of age; patients with relapsed ALL; and patients who did not have a signed informed consent. A total of 158 patients were included in the study, aged between 0 and 17 years. The information about patient characteristics and all variables was taken from the patients' files, where informed consent is mandatorily stored. Descriptive statistics were used to evaluate variables such as age, gender, leukocyte number, immunophenotype, prednisone response, risk group assessment, cytogenetics, relapse, and MRD. Kaplan-Meier curves were used to assess survival, for which patients were divided into two subcohorts: a 2011-2015 subcohort and a 2016-2020 subcohort. The statistical analyses used Prism version 10.2.3 (GraphPad Software, La Jolla, CA). For the analysis, we used Kaplan-Meier curves, the log-rank (Mantel-Cox) test, the log-rank test for trends, the Gehan-Breslow-Wilcoxon test, survival proportions, the chi-square test, and correlations.

Results: A shift in risk groups was observed after the introduction of MRD testing in 2017, with more patients being stratified in the medium-risk group (MRG) and high-risk group (HRG). At the survival analyses between bone marrow (BM) aspiration and MRD on day 15, we discovered that patients with MRD>10% had much higher overall survival (OS) and event-free survival (EFS) compared to patients with >25% blasts in the BM; 24(11.4%) patients relapsed, of which, nine (3.8%) were very early relapses and 10 (4.1%) were late relapses. The five-year OS and EFS for patients with the T-cell immunophenotype of ALL and those with leukocyte counts >100,000/mm were identical to those at one year.

Conclusions: The OS of the 2016-2020 subcohort was higher than that of the 2011-2015 subcohort, and more patients were stratified into MRG and HRGs due to the implementation of MRD testing. Minimal residual disease testing helped to improve significantly the survival rates of patients with more than 10% residual disease. None of the patients with very early relapses entered complete remission (CR), but all late relapses achieved CR. All events experienced by patients with the T-cell immunophenotype, or leukocyte counts of >100,000/mm occurred in the first year after diagnosis.