Research Updates — The Environment and Breast Cancer

Breast cancer is estimated to cause more than 40,000 deaths in the United States in 2014, according to the National Cancer Institute. In honor of Breast Cancer Awareness month in October, the National Institute of Environmental Health Sciences (NIEHS) within the National Institutes of Health is highlighting several breast cancer research advances that occurred this year as a result of the Sister Study.

The NIEHS-led Sister Study is the only long-term study of women ages 35 to 74 in the United States and Puerto Rico whose sisters had breast cancer. It will follow 50,000 women for at least 10 years to learn how the environment and genes may affect the chances of getting breast cancer. The Two Sister Study is a Sister Study offshoot and examines young-onset breast cancer.

The researchers determined that women who use solvents in their jobs may have a higher risk for breast cancer, especially if this use occurred before their first full-term childbirth. Solvents are chemicals in paints, adhesives, degreasing agents, and cleaning products. In addition to this workplace association, other scientists found that mom’s family history plays a role in breast cancer risk. They discovered that variations in genes inherited from the mother's side of the family may influence the development of breast cancer.

Sister Study researchers also established a link between breast cancer and changes in the pattern of DNA methylation, or the binding of chemical tags called methyl groups onto DNA. They observed that changes in DNA methylation become more common with increasing age, and these age-related methylation sites have been reported to be more common in individuals with a variety of cancers. To see how the process may work, watch this animation.

This page last reviewed on March 17, 2016