understanding the risks in breast cancer

All women are at risk for getting breast cancer. As you get older, your risk increases. Assuming you live to age 90, your risk of getting breast cancer over your lifetime is about 14%. That might sound scary, because it means that an average of about one out of every seven women will get breast cancer over a 90-year life span.

You can also look at it another way: A 14% risk means there's an 86% chance that you WON'T get breast cancer.

How much do risk factors and preventive factors change your risk?
Knowing what factors can increase or decrease your risk for breast cancer is important. But you probably want to know just HOW MUCH those factors change your risk.

If you hear that a certain treatment can reduce your risk by 40%, what does that mean?

To understand what the numbers mean about YOUR risk for breast cancer, the key terms to know are relative risk and absolute risk.

Relative risk is the number that tells you how much something you do, such as taking a pill, can change your risk, compared to your risk without taking that pill. Relative risk can be expressed in percentages and in "hazard ratios." If you do nothing new, your hazard ratio is 1.0—this means that your risk doesn't change. If you do something and your risk decreases by half, or goes down to 0.5, then you are half as likely to have the risk. But if your risk goes up, from 1.0 to 1.88, then you are 88% more likely to encounter the risk. If your risk goes up to 3.0, then you have a threefold (300%) increased risk of having the problem.

Absolute risk is the size of your own risk. Absolute risk reduction is the number of percentage points by which your own risk changes if you do something, like taking a pill. The size of your absolute risk reduction depends on what your risk is to begin with.

Example of risk going up for a woman with no history of breast cancer
Smoking is associated with an increased risk of breast cancer as well as other diseases.

After lumpectomy with clear margins, your risk of the breast cancer coming back in the same breast is about 30%. But if you choose to have radiation therapy after your lumpectomy, you can reduce your risk of the cancer coming back by two-thirds or 66%. This is the relative risk decrease.

Knowing how much your breast cancer risk changes with lifestyle changes and treatment options can help you and your doctor make the best decisions for YOU.

source: http://www.breastcancer.org/risk/understanding.jsp