Breast-feeding and risk of childhood acute leukemia

Background: Breast-feeding is well known to have a protective effect agains t infection in infants. Although the long-term effects of breast-feeding on childhood cancer have not been studied extensively, a protective effect ag ainst childhood Hodgkin's disease and lymphoma has been suggested previousl y from small investigations. In this study, we tested the hypothesis that b reast-feeding decreases the risk of childhood acute leukemia. Methods: A to tal of 1744 children with acute lymphoblastic leukemia (ALL) and 1879 match ed control subjects, aged 1-14 years, and 456 children with acute myeloid l eukemia (AML) and 539 matched control subjects, aged 1-17 years, were inclu ded in the analysis. Information regarding breast-feeding was obtained thro ugh telephone interviews with mothers. All leukemias combined, histologic t ype of leukemia (ALL versus AML), immunophenotype of ALL (early pre-B cell, pre-B cell, or T cell), and morphology of AML were assessed separately in the data analysis. Results: Ever having breast-fed was found to be associat ed with a 21% reduction in risk of childhood acute leukemias (odds ratio [O R] for all types combined = 0.79; 95% confidence interval [CI] = 0.70-0.91) , A reduction in risk was seen separately for AML (OR = 0.77; 95% CI = 0.57 -1.03) and ALL (OR = 0.80; 95% CI = 0.69-0.93), The inverse associations we re stronger with longer duration of breast-feeding for total ALL and AML; f or MO, M1, and M2 morphologic subtypes of AML; and for early pre-B-cell ALL . Conclusion: In this study, breast-feeding was associated with a reduced r isk of childhood acute leukemia. If confirmed in additional epidemiologic s tudies, our findings suggest that future epidemiologic and experimental eff orts should be directed at investigating the anti-infective and/or immune-s timulatory or immune-modulating effects of breastfeeding on leukemogenesis in children.