“Should I be screened with mammography for breast cancer?”
For women between 70 and 74 years of age:
However, with regular screening:
You may hear the risks or benefits of breast cancer screening described as either absolute or relative. But what does all this mean and how does it apply to you?
The main difference is that absolute risk takes into consideration the fact that whether or not you get screened or treated, you still have a baseline risk of dying of breast cancer: 1 in 146 or 0.68%. With regular screening that risk changes to: 1 in 217 or about 0.46%. Relative risk does not consider baseline risk in the same way and may lead to confusion about how regular screening reduces risk.
The absolute risk is simply the difference in risk between regular screening (0.46%) and no screening (0.68%): 0.68% − 0.46% = 0.22%
Therefore screening in women aged 70–74 reduces your absolute risk of dying of breast cancer by0.22%. So the absolute benefit of screening is 0.22%.
Relative risk only looks at the reduction of risk as a proportion of the total risk (so it doesn’t consider that you are already at risk of cancer, this can lead to larger values than absolute risk):0.22% ÷ 0.68% = 32%
Thus, screening in women aged 70–74 reduces your relative risk of dying of breast cancer by 32%. So the relative benefit of screening is 32%.
Among 100,000 women aged 70 to 74 who are screened every 2 years for 11 years:
Among 100,000 women aged 70 to 74 who are not screened for 11 years:
If we screened 450 women, aged 70–74 years, at average risk of breast cancer every two years for 11 years…