Triple-Negative Breast Cancer: Risk Factors

breast cancer in female body diagram

Breast cancer growth may be driven by the so-called female hormones, estrogen and progesterone, or by HER2. But some breast cancers are not driven by any of these; the ER/PR/HER2 negative cancers are sometimes referred to as “triple negative,” and represent among the most aggressive breast cancers. So why do these cancers occur? What are the risk factors for triple negative breast cancer?

Two of the largest studies to date look at triple-negative breast cancer, and have found some reproductive factors (pregnancy and multiple childbirth), obesity, and lack of physical activity to increase risk.

The Research: Both studies used data from more than 155000 women enrolled in the Women’s Health Initiative. Of the group, 307 developed triple-negative breast cancer after a follow-up of 8 years, and 2610 were found to have estrogen-receptor-positive (ER+) breast cancer.  Let’s look at each of these studies:

  1. In the first study, investigators found that obese women had a 35% higher risk (they were 1.35x more likely) for triple-negative breast cancer, as compared to women with the lowest body mass index (BMI).
  2. In the second study, the number of births affected risk for triple negative breast cancer: Women who had given birth to 3 or more children were at higher risk than women who had given birth to one child (hazard ratio 1.46).

My Take: Triple negative breast cancer appears to be a very different disease, compared to the other breast caner subtypes. While the hormonal changes of pregnancy makes the breast less susceptible to ER-positive breasy cancer, these mechanisms do not reduce the risk for triple-negative disease. The link between pregnancy and increased risk for triple-negative breast cancer may be due to an abnormal response of the breast to pregnancy. Obesity and physical inactivity, on the other hand, might increase risk bu affecting insulin-like growth factors or inflammatory changes in the breast. I’m Dr. Michael Hunter.

The small print: The material presented herein is informational only, and is not designed to provide specific guidance for an individual. Please check with a valued health care provider with any questions or concerns. As for me, I am a Harvard- , Yale- and UPenn-educated radiation oncologist, and I practice in the Seattle, WA (USA) area. I feel genuinely privileged to be able to share with you. If you enjoyed today’s offering, please consider clicking the follow button at the bottom of this page.

Available now: Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Both can be found at the Apple Ibooks store. Coming Soon for iPad:  Understand Breast Cancer in 60 Minutes; Understand Colon Cancer in 60 Minute; Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Thank you.

Reference: Cancer Epidemiol Biomarkers Prev. Published online March 1, 2011. Abstract; J Natl Cancer Inst. Published online February 23, 2011. Abstract; Medscape Medical News, 2011 WbeMD LLC.

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Harvard AB Yale MD UPenn Radiation Oncology Radiation Oncologist, Seattle area

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