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Breast Cancer Genetic Risks

According to official figures, only between 5-10% of breast cancer is caused by genetic influences. But even though the percentage is relatively low, the numbers are high enough to warrant many women and men seeking regular checkups. Yes, men get breast cancer, too. Only about 0.7% as often as women, but it does occur, killing about 12,000 men per year.

So, simply being female increases the odds of breast cancer relative to men by 133:1. One leading theory indicates that the most likely cause is the substantially higher percentage of estrogen and progesterone in females. These hormones play a role in cell growth and appear to be involved when that growth occurs uncontrollably, as in breast cancer.

One genetic factor that may not seem genetic at first blush is the increased risk that comes with aging. Growing older, at what rate and in what way, is heavily influenced by genetics. Genetics determines the kind of physiology we have and that in turn plays a prominent role in aging, as researchers in the field are finding out.

About 17% of invasive breast cancers occur in women in their 40s. But, a whopping 78% of those who contract the disease are in their 50s or older. That shouldn't be surprising by now. It's commonplace to observe that cancers are more likely the older one gets. Take care not to turn the statement around, though. It's not correct to say that 78% of women 50 or older get breast cancer. In fact, the number is about 1 in 12 or only 8%.

One major genetic risk factor, though, doesn't come from normal genes, but from gene mutations. The most common mutations are labeled BRCA1 and BRCA2. The genes affected participate in making proteins that prevent cells from growing abnormally. Mutations or changes in them alter that ability, opening the gate to increasing the odds of breast cancer. According to some studies, having the mutation puts the odds of developing breast cancer at up to 80%.

Those mutations are almost always inherited, not produced by environmental, diet or other controllable factors. Women who have a mother who have had breast cancer are therefore at higher risk for developing the condition themselves. Though, obviously, women don't inherit genes from a sister, having a sibling that has contracted breast cancer is an indicator of increased risk.

Another gene mutation that may play a role is the ATM (ataxia-telangiectasia mutation), involving a gene which plays a role in repairing DNA strands. Breast cancer risk is doubled when yet another, the CHEK-2 gene, mutates. Mutations in a gene called the p53 increase the odds, since it works to suppress tumor growth. Fortunately, these are all fairly low likelihood occurrences.

Until gene therapy becomes more advanced, there's nothing a woman or man can do to alter the genetic endowment they've received. But knowing the risk factors can provide information that is helpful in prompting diagnosis. Knowing you have a family history that contains an individual with Cowden Syndrome, for example, provides incentive to seek early and frequent checkups.