Overweight, Obesity, Diabetes, and Risk of Breast Cancer: Interlocking Pieces of the Puzzle

Abstract

We considered epidemiological data on overweight, diabetes, insulin, and breast cancer. Overweight is inversely related to premenopausal breast cancer, but there is definite evidence that, as compared with normal weight women, the relative risk (RR) for postmenopausal breast cancer is around 1.5 for overweight women and >2 for obese women, and that the association is stronger in elderly women. Overweight and obesity are strongly related to diabetes. Diabetes is associated with postmenopausal breast cancer, too, with summary RRs from meta-analyses of 1.15-1.20, but not with premenopausal breast cancer (RR, 0.9). There is no consistent evidence that fasting insulin is related to breast cancer risk. Thus, although overweight and obesity are strongly related to postmenopausal breast cancer, diabetes is only moderately related to it. Given the extent of the association, and the likely residual confounding by overweight, inference on causality for the diabetes-breast cancer relation remains open to discussion. The Oncologist 2011;16:726 -729

Risk of Breast Cancer by Individual Insulin Use: An International Multicenter Study

“…The results of computation of breast cancer risk for factors such as reproductive history, HRT, and oral contraceptives were consistent with previously reported data. We did not observe, however, a risk with obesity, which has been frequently associated with a higher risk of breast cancer (29). This may be explained by the fact that the majority of our patients (cases and control subjects) were overweight or obese.…”

Body Mass Index and Prognosis of Metastatic Breast Cancer Patients Receiving First-Line Chemotherapy

“…The relationship between overweight and increased breast cancer risk was consistently observed in postmenopausal women (4,5), whereas the association between body weight and premenopausal breast cancer risk is less clear (6)(7)(8). Several lines of evidence also suggest that increased body weight is associated with a worse prognosis: a shorter survival has been observed in obese women with early breast cancer (9)(10)(11)(12) and in those gaining weight after breast cancer diagnosis (13).…”

Mayor frecuencia de aberraciones cromosómicas en linfocitos expuestos o no a mitomicina C, de mujeres post-menopáusicas obesas en comparación con mujeres no obesas del departamento del Cauca, Colombia

“…En estudios de casos y controles se ha demostrado que los altos niveles de estrógenos podrían inducir el desarrollo de cáncer de mama y de endometrio (67). El exceso de peso generalmente está asociado con resistencia a la insulina y tiene como resultado altas concentraciones de glucosa en el plasma, que se transforman en ácidos grasos libres y se depositan continuamente en el tejido adiposo (68). La insulina proporciona un estimulo ovárico para la síntesis de estrógenos, lo que contribuye al exceso de esta hormona y provoca deficiencia de progesterona (26).…”