The Absolute Risk of Developing Breast Cancer vs the Relative Risk for Developing Breast Cancer

Being a woman is the biggest risk factor for developing breast cancer. As women age, the absolute risk of developing breast cancer increases.  We have all heard the 1 in 8 statistic.  We know that 1 out of every eight women has a risk of developing breast cancer.  But as a surgical oncologist, I need women to understand the difference between the Absolute Risk of developing breast cancer vs the Relative Risk for developing breast cancer.  I want my patients to feel in control during their entire journey.
Absolute Risk of Developing Breast CancerWhen I tell my patients about the risk of developing breast cancer, I mean “the absolute risk” that they are likely to get breast cancer or develop recurrence.  The term “risk” is used to refer to a number or percentage that describes how likely a certain event is to occur.  

• If your current age is 20, the probability of developing invasive breast cancer in the next 10 years is   .06%, or 1 in 1,732. This means that 1 in 1,732 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 1,732.
• If your current age is 30, the probability of developing invasive breast cancer in the next 10 years is .44%, or 1 in 228.
• If your current age is 40, the probability of developing invasive breast cancer in the next 10 years is 1.45%, or 1 in 69.
• If your current age is 50, the probability of developing invasive breast cancer in the next 10 years is 2.31%, or 1 in 43.
• If your current age is 60, the probability of developing invasive breast cancer in the next 10 years is 3.49%, or 1 in 29.
• If your current age is 70, the probability of developing invasive breast cancer in the next 10 years is 3.84%, or 1 in 26.

       (BreastCancer.org)
Basically the younger you are the lower your absolute risk while the older you are, your absolute risk for developing breast cancer increases. These numbers and percentages are averages for the whole population. 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.  When I see patients, I pay careful attention to risk factors such as family history.  Women who have inherited mutations in the genes known as BRCA1 or BRCA2 carry a higher absolute risk for developing breast cancer.  For women with a BRCA1 mutation, the risk of developing breast cancer by age 80 is 72%. For women with a BRCA2 mutation, the risk is a bit lower, at 69%.
Relative Risk of Developing CancerThe relative risk for developing breast cancer is basically reported by research studies, which often compare groups of women with different characteristics or behaviors to determine whether one group has a higher or lower risk of breast cancer than the other (either as a first-time diagnosis or recurrence).  Basically I want to empower my patients, to make If I make certain lifestyle choices that will impact their relative risk of developing breast cancer or having a recurrence.  The Relative Risk calculation is always a bit tricky and can easily be distorted. It is very important to have a clear understanding of the actual medical research rather than  jumbled interpretations of medical research.

There’s the famous study that links breast cancer to drinking two or more alcoholic drinks per day.  Summarily, women who have two or more alcoholic drinks each day have a have a 50% higher risk for developing breast cancer than non drinkers.  That is an astounding statistic and frankly dishonest. It is also unnecessary to burden a woman going through breast cancer with guilt. The truth is that women who drink two or more alcoholic beverages a day are NOT 50% more likely to develop breast cancer.  Women who already have a 12% absolute risk of developing beast cancer, increase their absolute risk by 1.5 (50% is .5 and the number one is used as a baseline-BECAUSE MATH) times if they consume 2 or more alcoholic beverages. (.12 x 1.5 is about .18 or 18%).  So out of the 12% of women who develop breast cancer, women who have two or more alcoholic drinks a day have an18% absolute risk of developing breast cancer.  When it comes to statistics, ignore the hype beasts and focus on the math.  
So now that I have explained the difference between absolute risk vs. relative risk, its important that women know there are many different factors can increase and/or decrease the absolute risk of developing breast cancer.  My next blog will discuss those factors.