Genetic Testing of Breast Milk May Help Determine Risk

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A small, very early study suggests that doing genetic testing on breast milk could help identify women with breast cancer and women at high risk for breast cancer. The results were published by the American Association for Cancer Research.

The researchers collected breast milk samples from both breasts from 230 women who had just had a baby and were producing breast milk (lactating). All the women were scheduled to have a breast biopsy because a suspicious breast area had been found. When breast milk is made, some breast cells make their way into the milk. These cells can be separated from the breast milk and analyzed.

The breast milk samples were tested for DNA methylation, a gene abnormality. DNA methylation has been linked to a higher risk of breast cancer as well as actual breast cancer in the body. The genetic test, called promoter methylation analysis, was done on three genes: RASSF1, GSTP1, and SFRP1.

The researchers compared the results of the genetic testing to the breast biopsy results.

In women with biopsies showing non-invasive breast abnormalities, DNA methylation levels of the SFRP1 gene were significantly higher in milk from the biopsied breast compared to milk from the opposite, healthy breast.

In 10 women with biopsies showing invasive breast cancer, DNA methylation levels of the RASSF1 gene were much higher in milk from the biopsied breast compared to milk from the opposite, healthy breast.

These results suggest that testing breast milk for DNA methylation abnormalities might be a good way to identify women who may have or may be more likely to develop a breast problem, including invasive breast cancer.

Other research has shown a link between breast cancer and DNA methylation abnormalities of nearly 36 genes, including the three genes tested in this study. Most women could have the test done during their childbearing years -- about 80% of women have at least one child and produce breast milk after birth. Knowing about any increase in the risk of breast health problems could help a woman develop a more aggressive breast cancer screening plan to find any possible problems as soon as possible.

Still, it's important to remember that this study was small and very early. Much more research is needed to better understand how DNA methylation testing of breast milk samples can be a screening tool for breast cancer and risk. About 80% of the women in the study agreed to long-term follow-up, which will allow the researchers to continue to study any links between each woman's DNA methylation test results and any breast health problems in the future.

Stay tuned to Breastcancer.org to learn about other new research findings that may lead to better ways to prevent, diagnose, and treat breast cancer.

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