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Researchers have identified another gene that, when mutated, may increase a woman's chance of developing breast cancer. When functioning normally, the CHEK2 gene helps repair damage to DNA. However, the new study finds that women who have an abnormal form of the CHEK2 gene face a higher-than-average risk of breast cancer. Researchers say that the risk of breast cancer from a mutated CHEK2 gene is much lower than that associated with previous identified breast cancer genes, BRCA1 and BRCA2. The finding is a significant scientific discovery and will help guide further research, though experts predict it will have little direct impact on the current treatment of breast cancer patients and those at high risk for the disease. A group British and Dutch researchers conducted the study in an attempt to understand other genetic factors involved with breast cancer risk besides the well-known BRCA1 and BRCA2 genes. The researchers studied 1,071 breast cancer patients who had a family history of the disease but did not have mutated forms of the BRCA1 or BRCA2 genes (mutated forms of BRCA genes increase the risk of breast cancer by 20% at age 40 and by over 80% at age 60). These patients were compared with a group of 1,620 healthy persons. The researchers found that 5.1% of women and 13.5% of men who had been diagnosed with breast cancer had a mutated form of the CHEK2 gene in the study while only 1.1% of healthy patients carried the abnormal gene. Thus, researcher Nazneen Rahman of the Institute of Cancer Research and his colleagues concluded that an abnormal CHEK2 gene doubles the estimated lifetime risk of breast cancer in women and carries a tenfold increased breast cancer risk for men. These elevated risks are still modest; researchers believe only 1% of the population carries mutated CHEK2 genes and only a small percentage of those carriers will develop breast cancer as a direct result. (Also, only 1% of all breast cancer cases occur in men). The study illustrates the increased emphasis on genetics in attempting to understand the causes of cancer. Experts say that CHEK2 is an example of a low-risk cancer gene, a type that has been suspected to exist for years. Rahman and his colleagues believe the mutated CHEK2 gene works with another yet unidentified gene to increase breast cancer risk. In practical terms, the researchers suggest their study results be interpreted with caution. An abnormal CHEK2 gene does not significantly raise breast cancer risk. Rather, the risk is comparable to a host of previously identified factors, such as early onset of menstruation (before age 12), late menopause (after age 50), or never having children. The risk of breast cancer is much higher in women with BRCA1 or BRCA2 gene mutations, for which genetic testing is available in select cases. For most women, the early detection of breast cancer is key to successfully treating the disease before it becomes life-threatening. To help detect breast cancer, all women 20 years of age and older should perform monthly breast self-exams and receive regular physician-performed clinical breast exams. In addition to these guidelines, the National Cancer Institute recommends that women 40 years of age and older also receive a screening mammogram every one to two years. Beginning at age 50, women should receive yearly screening mammograms. Women at high risk of breast cancer, (as determined by genetic analysis or family history) should talk to their physicians about special screening guidelines and other preventive options, such as the drug tamoxifen.
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