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Genes Determine Breast Cancer, Density

Women With Denser Breasts Likely Have Mothers, Sisters, With Breast Cancer
WebMD Health News

April 1, 2003 -- The same genes that determine a woman's breast density may also influence her risk of breast cancer.

A study, published in the April 2 Journal of the National Cancer Institute, shows that women with denser breasts were more likely to have sisters and/or mothers who have had breast cancer, reports lead researcher Elad Ziv, with the University of California, San Francisco Mount Zion Women's Health Clinical Research Center.

Ziv and associates analyzed the records of 8,665 women who had mammograms in San Francisco between 1997 and 2001. They found a significant association between denser breast tissue and a higher breast cancer risk and having close relatives with the disease.

During the study period, the participants provided information including family history of breast cancer and height and weight. And based on mammography readings, radiologists classified breast densities with scores of I to 4 -- 1 being a less dense breast with more fatty tissue, and 4 being denser, glandular tissue.

The researchers found that breast density was associated with age, menopause status, body mass index (BMI, a measurement of weight to height), and HRT use.

Women with higher-density breasts were likely to be younger, premenopausal, and have a lower BMI than women with lower density-breasts. When comparing women over 50, those with denser breasts (a score of 4) were more likely to be on HRT than women with less dense breasts.

And those who had denser breasts were more likely to have first-degree relatives -- mothers and sisters -- with breast cancer.

"Thus, the genetic factors that determine breast density may determine breast cancer risk," Ziv writes.

SOURCE: April 2, 2003 Journal of the National Cancer Institute.

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