October is breast cancer awareness month. We hear that having a regular mammogram cuts the risk of dying from breast cancer by as much as 20%. Sounds like a good reason for getting screening. But what do those numbers really mean?
This short video helps us understand how they arrive at this 20% number. And what about the flip side of mammograms like false positives? What about over-diagnosis and over-treatment and all that anxiety? Take a look. It’s only 2 minutes long.
Relative vs Absolute risk
I’ve discussed the difference between relative and absolute risk before, so for more information on this, take a look at this post: https://calmerme.com/understanding-risk-in-cancer-research/
Remember that just about all the data you will see in the media will use relative risk. So you will hear the 20% risk reduction for mammogram use. It is extremely rare that they will report that without mammograms 5 women out of 1000 will die of breast cancer while with mammograms 4 women out of 1000 will die. That absolute difference is 1 woman in 1000. But the relative difference makes it appear much better as it ignores the 1000 women and just compares 4 women to 5 women with and without mammograms. And they don’t mention the false positives and overtreatment associated with mammography. (See the new Nordic study 2017 on mammography and over diagnosis)
It is confusing. And not just for mammograms – but for all treatments and procedures.
Talk to your doctor or healthcare professional about this if you are concerned or email me. Weighing up the risks and benefits of procedures/treatments vs over-treatment/false positives are important. But also worth considering is other risk factors and whether, if you don’t have mammograms, you will be more anxious. It isn’t just a black and white number decision. It is a very personal decision.
If you do have annual mammograms it may be worth considering joining the WISDOM study. This means your mammogram can help others too. It will help clarify the optimal frequency of mammograms for different risk groups of women.
And if you chose not to have regular mammograms, make sure you do self-examinations. Remember to look after your lemons.