Understanding Breast Cancer Risk

All women are at risk for breast cancer -- and most of us think our risk is higher than it actually is.

The commonly cited statistic – that women have a 1 in 8 lifetime risk of breast cancer – is a bit misleading because 1 in 8 women in the United States do not actually get breast cancer. The 1 in 8 number is an estimate of lifetime risk. A woman with average risk has a 1 in 8 chance of getting breast cancer sometime during her life if she lives to be 90. Some women are less likely to get breast cancer, and some have a greater risk. Some will not live to be 90.

A more meaningful way to look at risk is the chance of getting breast cancer during each decade of life. A woman in her twenties has a 1 in 1,837 (0.05%) risk of getting breast cancer, and her risk increases as she ages to a maximum in her seventies of 1 in 26 (3.88%). If you add up the percentages for each decade, you get 13% lifetime risk (1 in 8). During no ten-year period during her lifetime, though, does a woman face a risk of getting breast cancer as high as 1 in 8.

Of course, some women are at greater risk of developing breast cancer. And they, too, overestimate their risk for getting this disease.

Women with a faulty breast cancer gene are said to have “up to” an 85% lifetime risk of getting breast cancer, but according to the National Cancer Institute, the risk ranges from 36% to 87%. As with women who have an average risk, their chance of getting breast cancer increases as they age. (The exception to this is women with close relatives who got breast cancer when they were young.)

Others with a higher than average risk for breast cancer are women diagnosed with precancerous conditions like lobular carcinoma in situ or atypical hyperplasia. Women who have had breast cancer or ductal carcinoma in situ, a noninvasive cancer, are also at increased risk.
It should be noted that many women who are high risk will never get breast cancer. No one knows why they don’t or why some women get breast cancer even though they have no risk factors. The interplay of genetic make-up, age, reproductive history, environmental exposures, and lifestyle determines whether or not we develop breast cancer.

But those of us who are high risk can’t help feeling we’re destined to get breast cancer. Some choose overly aggressive treatment because they can’t live with the possibility that they might get this disease. They get bilateral mastectomies, reducing their risk by 90%. In some cases, this surgery is more drastic treatment than is necessary, and it does not guarantee they will never get breast cancer.

Women do it to ease their fears. Being high risk for breast cancer is more frightening than it should be because of misperceptions about the level of risk for the average woman.