By now you may be familiar with the statistic that says 1 in 8 women will develop breast cancer. In each decade of life, the risk of getting breast cancer is actually lower than 13% for most women.
For you, a 1-in-8 lifetime risk may seem like a high likelihood of getting breast cancer. Even though studies have found that women have a 13% lifetime risk of developing breast cancer, your individual risk may be higher or lower than that.
When we talk about factors that can increase or decrease the risk of developing breast cancer, either for the first time or as a recurrence, we often talk about two different types of risk: absolute risk and relative risk.
Absolute risk
Absolute risk is used to describe an individual’s likelihood of developing breast cancer. It is based on the number of people who will develop breast cancer within a certain time period. Absolute risk also can be stated as a percentage.
When we say that 1 in 8 women in the United States, or 13%, will develop breast cancer over the course of a lifetime, we are talking about absolute risk. On average, an individual woman has a 1-in-8 chance of developing breast cancer over an 80-year lifespan.
The absolute risk of developing breast cancer during a particular decade of life is lower than 1 in 8. The younger you are, the lower the risk. From age 30 to 39, absolute risk is 1 in 233, or 0.43%. This means that 1 in 233 women in this age group can expect to develop breast cancer. Put another way, your odds of developing breast cancer if you are in this age range are 1 in 233.
From age 40 to 49, absolute risk is 1 in 69, or 1.4%.
From age 50 to 59, absolute risk is 1 in 38, or 2.6%.
From age 60 to 69, absolute risk is 1 in 27, or 3.7%.
As you can see, the older you are, the higher your absolute risk of breast cancer. Your individual breast cancer risk may be higher or lower, depending on a number of factors, including family history, reproductive history (such as menstrual and childbearing history), race/ethnicity, and other factors.
The absolute risk of breast cancer is much higher for women who have inherited mutations in the genes known as BRCA1 or BRCA2. Their absolute risk over the course of a lifetime ranges from 40-85%. This means that your absolute risk of having the breast cancer come back within 5 years is 10%, or 1 in 10. Relative risk
Relative risk is a number or percentage that compares one group’s risk of developing breast cancer to another’s. Understanding relative risk can help you answer an important question: If I make certain lifestyle choices or have certain treatments, how much will I increase or decrease my risk of developing breast cancer or having a recurrence?
Example of breast cancer risk going up
Many studies have shown that women who have two or more alcoholic drinks each day have a higher risk of developing breast cancer. Compared to women who do not drink, women who have two or more drinks per day have a 25% higher risk of breast cancer. Compared to women who do not drink, women who have two or more drinks per day have a relative risk of 1.25. The .25 describes the relative increase in risk for the other group; it is another way of expressing the 25% higher lifetime risk (25% = .25).
Another way of saying this is that women who drink two or more alcoholic drinks per day have 1.25 (1 + .25 = 1.25) times the risk of developing breast cancer than women who do not drink.
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