Plasma leptin levels and risk of breast cancer in premenopausal women
Couplée à la cohorte “Nurses' Health Study II”, cette étude (330 cas et 636 témoins) évalue l’association entre le niveau plasmatique de leptine et le risque de cancer du sein chez des femmes non ménopausées
Background: Body mass index (BMI) is inversely related to the risk of premenopausal breast cancer, but the underlying biological mechanisms of this association are poorly understood. Leptin, a peptide hormone produced primarily by adipocytes, is a potential mediator of the BMI association since BMI and total body fat are positively associated with circulating leptin levels and leptin and its receptor are overexpressed in breast tumors. Methods: We conducted a prospective case-control study nested within the Nurses' Health Study II cohort examining the association between plasma leptin levels in premenopausal women and breast cancer risk. Leptin was measured in blood samples collected between 1996 and 1999. The analysis included 330 incident breast cancer cases diagnosed after blood collection and 636 matched controls. Logistic regression models, controlling for breast cancer risk factors, were used to calculate odds ratios (OR) and 95% confidence intervals (95% CIs). Results: After adjustment for BMI at age 18, weight change since age 18 to blood draw, and other breast cancer risk factors, plasma leptin levels were inversely associated with breast cancer risk (OR for top vs. bottom quartile 0.55; 95% CI 0.31-0.99; p for trend=0.04). Adjustment for BMI at blood draw attenuated the association (OR=0.69; 95% CI 0.38-1.23; p for trend=0.26). Conclusion: Our results suggest that leptin may be inversely associated with breast cancer risk, but it is unclear whether any part of this association is independent of BMI.