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Most breast cancer occurs in women without a mutation in BRCA or other genes that increase cancer risk. And not every woman with an inherited mutation in one of these genes will get breast cancer. There are many factors that can affect risk for hereditary or sporadic breast cancer.
For women with a BRCA mutation there is some evidence that the location and type of BRCA mutation can influence breast cancer risk but more research needs to be done to better understand the link between type of mutation and cancer risk.
Research has linked physical activity during the teen years, normal weight at menarche, and normal weight at age 21 with later onset of breast cancer in women with BRCA mutations. Exercise and a maintaining a healthy weight have other health benefits as well. Staying active is always a good idea. Visit our page on exercise for more information.
Research suggests that other genes can affect breast cancer risk in women with BRCA mutations. Changes in other genes, known as single nucleotide polymorphisms or SNPs, have been shown to slightly increase breast cancer risk in women without hereditary cancer mutations and might also be linked to breast cancer risk in BRCA carriers. Among the women who carried normal copies of these genes, the risk for breast cancer appeared to be at the lower end of the 50-85% breast cancer risk range. Of the BRCA-positive women who had two abnormal copies of these SNPs, lifetime risk for breast cancer was at the high end of the risk range. Women with one abnormal copy of the SNPs seemed to have a risk in the intermediate range. This research is still in early stages and is not yet being used to personalize breast cancer risk.
Other factors can increase breast cancer risk in women without a mutation. Some of these factors also may have similar effects in women with mutations.