If that is the case (2% increase in risk of cancer), and a woman starts getting these at 40, by the age of 75, she has double her risk of breast cancer.
Does it increase the risk by 2 percent (meaning if it was 1 in 100 chance its now 1.02 in 100), or by 2 percentage points (meaning if its one in 100, its now 3 in 100). I suspect the former (although not specifically 1.02 in 100, the risk is I think higher, I just uses those numbers as easy examples of the concept).
Either way its not necessarily additive. If one x-ray moves you from 1 to 1.02, a 2nd may not move you to 1.04. If one moves you from 1 to 3, a 2nd may not move you to 5. It may be more than additive or less, or it may start out one way and then chance to the other. (For example you might increase the risk by a certain amount, then further radiation may increase it by a larger amount than the first increase as damage accumulates, but then even more radiation is likely to reduce the increase in risk, as those who are likely to get cancer already have it, as its possible that the radiation kills some cancer.) |
