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Research Looks at Link Between Bone Density and Risk

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A study suggests that the stronger a postmenopausal woman's bones are, the more likely she is to develop breast cancer.

The study looked at the health histories of almost 10,000 women, with an average age of 63. During more than 8 years of follow-up, 327 women were diagnosed with breast cancer.

All of the women in the study had DEXA scans to measure bone mineral density. Bone mineral density is a measure of bone strength and is reported as a T-score. The higher the T-score, the stronger the bones. The women also had their breast cancer risk estimated using the Gail score tool. A Gail score estimates a woman's risk of developing breast cancer in two time frames:

  • the next 5 years
  • over a lifetime

based on several personal and health factors, including age, race, age at first pregnancy, and number of relatives with breast cancer. A Gail score is reported as a number.

In this study, postmenopausal women with lower T-scores and Gail scores were less likely to develop breast cancer than women with higher T-scores and Gail scores. Women diagnosed with breast cancer were more likely to have a high T-score (stronger bones), a high Gail score, or both. Having both a high T-score and a high Gail score was linked with the highest risk of breast cancer.

Still, these results are EARLY results and shouldn't be applied to all women. This study didn't try to figure out why breast cancer risk is higher for postmenopausal women with strong bones. Because estrogen levels affect both bone health and breast cancer risk, it's likely that estrogen levels might be part of the answer.

The hormone estrogen keeps bones healthy, so women with higher estrogen levels before and after menopause are more likely to have stronger bones. But estrogen also can encourage the growth and development of hormone-receptor-positive breast cancer cells. So the higher estrogen levels that keep bones healthy may increase breast cancer risk.

This study doesn't mean that having strong bones after menopause is a bad thing. Strong bones help you move around easily and support your body. Strong bones also make it less likely that you'll experience a bone fracture as you get older. The study results suggest that if you're a postmenopausal women with high bone mineral density and are at high risk for breast cancer, you may want to talk to your doctor about setting up a more aggressive breast cancer screening plan for your unique situation. Your plan may include screening more than once a year and using other screening techniques, such as ultrasound and MRI, as well as an annual mammogram.

An interactive version of the Gail score tool is online at the National Cancer Institute Web site. Visit the Breastcancer.org Bone Health section to learn more about bone health and bone mineral density.

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