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Changes in Breast Density Alter Breast Cancer Risk

Posted Jun 24 2010 7:27am
Breast density is one of the most well known risk factors for breast cancer.  Research has confirmed over and over that high breast density can increase the risk for breast cancer by 5-fold or more compared to low breast densities.  What is probably not as well known is that breast density appears to be modifiable and can change over time.  New research presented at the 101st Annual Meeting of the American Association for Cancer Research reports that changes in mammogram-measured breast density can alter a woman's breast cancer risk.

In one breast cancer study , breast density information was collected from women 35 years of age and older without breast cancer who took part in a large mammogram health study.  From this group of women, the researchers collected and analyzed data from 219 women who developed breast cancer and 1,900 women who did not develop breast cancer.  The results of this analysis showed that
  • Women whose breast density decreased one category or more over an average 6-year period had nearly a 30% reduction in breast cancer risk.
  • In contrast, women whose breast density increased one category or more had a 50% increase in breast cancer risk.
So, what can cause a woman's breast density to change over time?  One factor appears to be estrogen + progestin hormone replacement therapy.  A second breast cancer study at this conference used data from the well known Women's Health Initiative Study to examine the effect of estrogen + progestin therapy on changes in mammogram-measured breast density.  Mammogram screenings were conducted at the beginning of the study and 1 year later; the effect that changes in breast density had on breast cancer risk were determined.  The results showed that
  • In women not receiving estrogen + progestin therapy, 57% showed a decline in breast density and 47% showed only a modest increase.
  • Of the women who were on estrogen + progestin therapy, 84% experienced an increase in breast density after one year and only 16% showed a decrease in breast density.
  • Women who showed an increase in breast density of more than 19% were about 3.5 times more likely to develop breast cancer compared to the women with the lowest increase in breast density.
These are significant findings.   Not only do these studies show that breast density can change over time, they also report that these changes can alter a woman's risk of breast cancer with an increase in breast density increasing breast cancer risk.  According to an article in the Los Angeles Times , many women are not informed of their breast density measures even though these are typically available with every mammogram.  Being able to track your personal breast density over time is a valuable tool in determing your risk of breast cancer.  Just as important is making changes that might help reduce your breast density over time.  It has been suggested that tamoxifen can reduce breast density, which is probably one of the ways it might act as a breast cancer prevention drug.  Some studies suggest that diet might also effect breast density with breast density being increased by diets high in saturated fat; however, these studies are inconsistent.  More thorough investigations into diet and lifestyle changes that might decrease breast density are needed.

Read my book Fight Now: Eat & Live Proactively Against Breast Cancer to learn more about diet and lifestyle changes you can make to reduce your personal risk for breast cancer.
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