A study carried out on approximately 9,000 Danish residents revealed that a specific mutation in the CHEK2 gene might increase three-fold a woman's risk of developing breast cancer in her lifetime. The study, which was the first to examine the prevalence of the CHEK2 mutation and the cancer risk associated with it, in the general population, will be published in the July 31 edition of the Journal of Clinical Oncology.
"Our study shows that women in the general population who carry a specific CHEK2 mutation are three times as likely as women without the mutation to develop breast cancer," said Borge G. Nordestgaard, MD, Professor and Chief Physician, Department of Clinical Biochemistry, Herlev University Hospital, Denmark, and lead author of the study. "The findings suggest that CHEK2 could serve as a useful biomarker for identifying women who would benefit from heightened, regular screening for breast cancer."
CHEK2, which belongs to a class of genes known as "tumor suppressors," is responsible for repairing DNA damage and preventing the uncontrolled division of cells, which can lead to cancer. In this study, researchers looked for a specific mutation, known as CHEK2*1100delC, which impairs the gene's ability to fix damage to DNA.
Previous case-control studies have shown an association between this specific CHEK2 mutation and breast, prostate, and colorectal cancer. Researchers designed this study to assess the prevalence of the mutation in the population at large and to examine its impact on cancer risk.
Dr. Nordestgaard and his colleagues randomly selected 9,231 Danes who had participated in the Copenhagen City Heart Study--a cohort of more than 20,000 Danish men and women that followed were monitored for an average of 34 years for cancer development.
The researchers found that 0.5% of all participants carried the CHEK2 mutation. Among women who carried the CHEK2 mutation, 12% developed breast cancer, compared to 5% of non-carriers. Adjusting for other factors, such as age, body mass index, and use of hormone replacement therapy, researchers found that women who carried the mutation were 3.2 times as likely as women who had normal CHEK2 genes to develop breast cancer. Those most at risk were mutation carriers on hormone replacement therapy who were more than 60 years old and overweight--who had a 24% chance of developing the disease within 10 years. The researchers found no statistically significant association between the CHEK2 mutation and prostate, colorectal, or general cancer risk.
By way of comparison, other studies have shown that BRCA 1/2 mutations occur in roughly 1% of the general U.S. population. Women with a BRCA1 or BRCA2 mutation have a dramatically heightened risk of developing breast cancer--up to an 80% chance of developing the disease during their lifetime and at a much younger age than women who do not have one of these two mutations. Life-time risk of breast cancer among women in the general population is approximately 13%.
"There are clearly a number of genetic and environmental factors in play when it comes to the development of breast cancer," said Dr. Nordestgaard. "The identification of CHEK2 as a biomarker gives us a better picture of the genetic risk factors, and may help to identify a significant subset of women who would benefit from more vigilant screening for the disease."
According to the study's authors, a key limitation of the research was that it included only white Danish women; it is not known to what extent CHEK2 mutations are found among black, Hispanic or other women, or whether the breast cancer risk associated with CHEK2 mutations among these women is of a similar magnitude to those involved in this study.