Overweight and Obesity as Prognostic Factors for Survival in Children With Acute Lymphoblastic Leukemia

Data collection Information regarding sex, age at diagnosis, place of residence, white blood cell (WBC) count, immunophenotype (B or T lineage), weight and height (length when appropriate) at diagnosis, and chemotherapy protocol is collected from the patients' clinical charts by previously standardized staff. Overcrowding was used as a proxy for socioeconomic status (SES) according to the Bronfman's criteria (high SES, up to 1.5 people per room; medium-low SES, more than 1.6 people per room). The risk classification is according to the criteria of the National Cancer Institute (NCI): standard risk [ages from 1 to 9.99 years; WBC count < 50 × 109/L] or as high risk [age < 1 or ≥ 10 years or WBC ≥ 50 × 109/L].

Assessment of nutritional status at diagnosis of ALL BMI at diagnosis will be used.. Using WHO software (version 3.2.2, World Health Organization, Geneva), the BMI-for-age Z-scores were calculated for each patient. According to WHO classification, patients were categorized as normal (- 1.9999 to 0.9999), wasted (- 2 to - 2.9999), severely wasted (≥ - 3), at risk of overweight (1-1.9999), overweight (2 to 2.9999) and obesity (≥3). In addition, the BMI percentiles cutoffs provided by CDC were: normal (p5-84.9999), underweight (< p5), overweight (p85-94.9999), and obese (≥ p95). The nutritional classification and measurements validation regarding weight and height recorded in clinical files used to classify patients' nutritional status in present research has been previously described. Underweight patients were excluded from the analyses.

Sample size The sample size calculation was performed using Epi-Info version 7 software taking into account a mortality outcome frequency of 10.8% in the unexposed group (normal weight patients) and a death outcome frequency of 24% for the exposed (obese/overweight patients), a statistical power of 80% and a confidence of 95%; resulting in a total "n" of 350 overweight/obese patients to be compared with the rest of the cohort that are not overweight and obese.

Statistical analysis Descriptive statistics and relative risks (RR) calculation with 95% confidence intervals (CI) will be carried out. Kaplan-Meier survival analysis will be conducted. Log-rank test will be calculated. The analyses will be conducted independently for disease-free-survival (DFS) or overall survival (OS), adjusting for variables whose effects on the studied outcomes have been previously documented (age, sex, socioeconomic status, immunophenotype, NCI risk classification, and chemotherapy protocol). A Cox proportional hazard model will be used. Hazard ratios (HR) with 95% CIs will be calculated.