SCIENCE: Genetics and Breast Cancer
Published 10 Dec 2015
A new study published in Cancer Epidemiology Biomarkers and Prevention last month(1) estimates that the liability to breast cancer associated with our genetic background (or “family history”) is around 31%, slightly more than the 27% estimated by a similar, but smaller study, published in 2000 (2).
The research uses data from the Nordic Twin Study of Cancer (NorTwinCan) data set. This is the largest twin study data set in the world, and enables research into the hereditary and familial (genetic) risk of cancers, including breast, prostate, ovarian, and colon cancers.
The current analysis is based on approximately 21,000 identical and 31,000 non-identical female twin pairs and included 3900 woman diagnosed with breast cancer. The study found that at every age, breast cancer risk among identical twins whose co-twin had breast cancer was higher compared to the overall incidence, confirming the importance of our genetic background.
These results provide conclusive evidence that genetic differences between women explain a substantial portion of the variation (an estimated 31%) in liability to develop breast cancer. But this figure does not represent the full story about genes and breast cancer. A 2003 study (3) found that the risk of getting breast cancer by the age of 50 for woman carrying a BRCA mutation born before 1940 was 24%, but for those born after 1940 was 67%. This shows that carrying a gene does not inevitably result in disease; the gene interacts with its contemporary environment and modern environments contain factors that increase the likelihood of cancer developing.
The study by Möller et al. highlights the importance of genetic background in diseases such as breast cancer. But we should not forgot that breast cancer is a result of an accumulation of changes (mutations and epigenetic alterations) which occur as a result of our environment and our genes. Currently; we cannot do anything about our inheritance but we can do something about our environment and the chemicals that pollute it.
1. Möller et al. (2015). The Heritability of Breast Cancer among women in the Nordic Twin Study of Cancer. Cancer Epidemiology Biomarkers and Prevention cebp.0913.2015; Published OnlineFirst November 10, 2015 http://cebp.aacrjournals.org/gca?gca=cebp%3B1055-9965.EPI-15-0913v1&submit=Get+All+Checked+Abstracts
2. Lichtenstein et al. (2002). The New England Journal of Medicine 343(2): 78-85
3. King et al. (2003). Breast and ovarian cancer risks due to inherited mutations in BRCA1 and BRCA2. Science 302(5645): 643-646