It has been hypothesized that diabetes may influence the risk of breast cancer (BC) by impaired regulation of the insulin and insulin-like growth factors (IGF) pathways. Current evidence supports a reduction in BC risk by doing regular physical activity due, in part, by reducing insulin resistance and improving glucose control. Material and Methods

A population based case control study was conducted to evaluate the association between insulin resistance and diabetes mellitus on the risk of BC in Mexican women. A total of 1000 incident cases and 1074 matched controls to cases by five years of age, site and health institution were analyzed. Women provided information on health, diet and physical activity by means of a face to face interview; information about the family history of diabetes mellitus and whether or not women were diagnosed with this disease. Anthropometric measurements and blood samples were obtained from all women. A conditional logistic regression model was used to assess this association. Results

In postmenopausal women, there was an interaction between physical activity and diabetes mellitus on the risk of BC. The effect of diabetes mellitus type 2 decreased with increasing moderate physical activity (OR = 3.67, 95% CI 1.78 — 7.58; OR = 2.86, 95% CI 1.37 — 5.96; OR = 0.82, 95% CI 0.19 — 3.59, by increasing tertiles of daily hours of moderate physical activity respectively); in premenopausal women, this association was not statistically significant (OR = 1.55, 95% CI 0.86-2.79), however in a subsample of premenopausal women, an increase was observed in the risk of BC per unit change in the increase of C-peptide, an indirect marker of insulin resistance (OR = 1.98, 95% CI 1.41 - 2.76). Discussion

The results of this study are consistent with numerous mechanisms linking physical activity directly to reduce BC risk probably, in part, through reducing insulin resistance and improving glucose control.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-09-05.