Dietary Glycemic Index and Glycemic Load and Risk of Breast Cancer by Molecular Subtype in Mexican Women.

The objective was to estimate the risk of breast cancer (BC) molecular subtypes in relation to the average glycemic index (GI) and the dietary glycemic load (GL) in Mexican women. From 2007 to 2011, a study of incident cases and population controls was conducted in five states of northern Mexico. A subsample of 509 cases matched 1:1 by age with 509 controls was selected. With a food frequency questionnaire, information about diet was obtained, and GI and GL were calculated. The expression of human epidermal growth factor receptor 2 (HER2), and estrogen (ER) and progesterone (PR) receptors in tumors was obtained from medical records. Patients were classified as luminal A (RE+ and/or PR+/HER2-), HER2+ (RE+ and/or PR+/HER2+ and RE-/PR-/HER2+), or triple negative (TN) (RE-/PR-/HER2-). GI and GL associations with BC molecular subtypes were evaluated using conditional logistic regression models. GI was positively associated with luminal A (OR= 1.12; 95% CI: 1.03, 1.22), HER2+ (OR= 1.15; 95% CI: 1.02, 1.30), and TN (OR= 1.20; 95% CI: 1.03, 1.39) BC. GL was not associated with BC molecular subtypes. These results suggest that the type of carbohydrate consumed is associated with increased BC regardless of the luminal A, HER2+, and TN subtypes.