We analyzed data from 4356 patients with ALL diagnosed from 1988 to 1995 at age 2–20 years and enrolled in CCG studies 1881, 1891, 1922, 1882 or 1901. Patients with Down Syndrome and those with CNS disease at diagnosis were excluded. Obesity was defined as a body mass index (BMI)>95th percentile by the Center for Disease Control growth charts (www.cdc.gov/growthcharts). Obesity at diagnosis did not affect outcome in patients younger than 10 years but independently predicted 5y risk of leukemia relapse and event free survival (EFS) in the 1026 patients aged 10 years or older. Multivariate analysis in patients aged 10 years or older showed that obese patients had increased risk of leukemia relapse (hazard ratio-HR- 1.5, p=0.013) and of all the events (HR 1.5, p=0.009). Other independent predictors of poor outcome were high WBC at diagnosis and failure to achieve bone marrow M1 status by day 7 of therapy. Age had borderline significance; sex, race and type of therapy were not significant. To assess whether the effect of obesity on outcome was due to absolute body weight, we studied the effect of weight in Kg at diagnosis in patients aged 10 years or older. Patients >60kg had increased risk of leukemia relapse (HR 1.4, p=0.002) and of all the events (HR 1.4, p=0.006). High WBC at diagnosis and bone marrow status at day 7 maintained their significance; age, sex, race and therapy were not significant. The effects of obesity and weight on outcome only partially overlapped: obesity still predicted outcome when only patients <60 kg were analyzed as well as weight >60 kg predicted outcome when obese patients were excluded from the analysis. Obesity and weight >60 kg at diagnosis were not associated with differences in early toxic deaths, lenght of initial phases of therapy or days of hospitalization. In conclusion, preadolescents and teenagers with ALL who were either obese or >60 kg of weight at diagnosis had higher risk of leukemia relapse and poorer EFS.

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