Obesity Increases Triple Negative Breast Cancer Risk
Posted Mar 04 2011 10:11am
Numerous studies have shown that there is a link between being overweight or obese and increased breast cancer risk. In fact, some of these studies have reported that obesity is linked to an increase in overall breast cancer risk, increased risk for advanced stages of breast cancer upon diagnosis, increased risk of developing breast cancer in the second breast, and decreased breast cancer survival. However, a lot less is known about the impact of obesity on triple negative breast cancer.
Information from patients who participated in the Women's Health Initiative trial was assessed for a possible link between obesity and two subtypes of breast cancer , estrogen receptor-positive (ER+) breast cancer and triple negative breast cancer. Of the 155,723 women enrolled in the Women's Health Initiative trial, 2,610 were diagnosed with ER+ breast cancer and 307 developed triple negative breast cancer. Analysis of these data showed that
Women with a body mass index (BMI) in the highest quarter showed a 35% increased risk for triple negative breast cancer compared to women with a BMI in the lowest quarter.
Women with a higher BMI had a 39% increased risk for ER+ breast cancer.
Waist and hip sizes were both linked to ER+ breast cancer, but not to triple negative breast cancer.
Women with the highest level of physical activity had a 23% decreased risk for triple negative breast cancer and a 15% decreased risk for ER+ breast cancer.
This is an interesting study that shows a somewhat surprising link between obesity and triple negative breast cancer. In general, it has been thought that obesity was linked primarily, or perhaps more strongly, with ER+ breast cancer because of the amount of estrogen produced by body fat. In fact one study reported that adult weight gain doubled ER+/PR+ breast cancer risk but only increased ER-/PR- breast cancer risk by 33%. This new study would suggest that obesity probably is linked to breast cancer through multiple mechanisms and as such can increase breast cancer risk through more than just the production of estrogens. These other factors likely include growth factors and inflammatory factors; however, further research will be needed to develop a clearer understanding of the link between obesity and triple negative breast cancer.