METHODS
This was an international, multicentric retrospective cohort study. Ten Latin-American oncologic centers providing care to children and adolescents with LLy participated, collecting and recording the clinical data of their patients. As a retrospective study of de-identified secondary use of clinical data the St. Jude IRB determined an exempt research status, and this determination was provided to the site principal investigator for local study submission and approval at each one of the participating institutions.
Study inclusion criteria were a diagnosis of LLy of any phenotype between January 1, 2007 and December 31, 2017; age less than 19 years; and clinical medical records available for review and abstraction. For each patient variables collected included age, gender, lymphoma immunophenotype, stage and sites of disease, treatment regimen administered and clinical status. Data was collected in a case report form and then transcribed to an electronic password-secure REDCap database. Study staff at St. Jude periodically reviewed the data entered and queried sites for missing data or for clarifications. Online meetings were held for training, progress evaluation and other discussions.
Statistical analysis
Event-free survival (EFS) was calculated from the time of diagnosis until death, relapse, progression, abandonment or the occurrence of a second malignancy. Patients with no events were censored at the date of last follow-up. Overall survival (OS) was defined as time from diagnosis to death or date of last follow-up for those who were still alive. The EFS and overall survival (OS) were calculated using the Kaplan–Meier method, and groups were compared using a log-rank test. Induction deaths were defined as those occurring in the first 30 days after admission, before remission evaluation. Deaths in complete remission included those attributed to any cause other than LLy after achieving a complete remission. Abandonment was defined as failure to adhere to scheduled or unscheduled visits during therapy for at least four consecutive weeks. Follow-up was updated as of March 1, 2020, thus each patient had at least 3 years of follow-up.
Categorical data are expressed in absolute frequencies and percentages. Continuous variables are expressed as medians (range). The χ2 or Fisher exact test was used for the analysis of categorical variables and Mann-Whitney test for continuous variables.