"Can Mammogram Radiation Cause Breast Cancer?"
Over the last few decades our radiation exposure has nearly doubled,
thanks almost exclusively to
medical sources such as CT scans.
We've known that higher dose radiation, like CT scans and angiograms,
can cause breaks in our DNA, but now we know that mammograms can, too.
You can find X-ray induced DNA damage in white blood cells
drawn from a woman right after her mammogram.
That's amazing they can find evidence of DNA break.
I mean, how much blood is there in the breast in the first place,
and then you squeeze it out during the procedure,
and then it mixes with the unexposed blood from the rest of the body
and you can still pick up the DNA damage
circulating throughout her system.
So what they found underestimates the DNA damage in the breast tissue itself.
But doctors tell women there's nothing to worry about.
Just a few extra cases of breast cancer
are caused by mammograms. Wait, what?
Mammograms causing breast cancer?
Yes. The risk of radiation-induced breast cancer from modern,
low dose digital mammograms depends on how often
you get screened, and at what age you start.
For a group of 100,000 women screened annually from age 40 to 55 years
and every other year until age 74, it's predicted that there will be
86 cancers induced and 11 deaths due to radiation-induced breast cancer.
Meaning they estimate 11 of those women will die from breast cancer
that they would never have gotten if they decided
not to get mammograms, not expose themselves to that radiation.
They even calculated the lifetime risk of developing a radiation-induced
breast cancer after just getting a single mammogram.
Women with large breasts may carry additional risk
because their mammograms may require additional views
and the greater radiation doses are expected to translate
into a greater risk for radiation-induced
breast cancer and breast cancer death.
As much as triple the lifetime
attributable risk of developing breast cancer
because of the mammogram radiation exposure.
The earlier one starts screening, the higher the risk as well,
since there's more time for a cancer to grow.
This comes up for women with BRCA gene mutations,
for whom screening is sometimes recommended starting in their twenties.
But at that age, mammograms may cause
as many breast cancer deaths as they prevent.
A net benefit would be expected at 35 years old though,
and likely the same for women without BRCA mutations.
Yes, the risk of radiation-induced cancer from mammography is not negligible,
but "the potential for mortality benefit is generally considered
to outweigh the risk of death from radiation-induced
breast cancer attributed to mammography screening,"
a benefit-to-risk ratio in lives of 10 to 1 or more.
Now these estimates on how much breast cancer mammogram
X-rays may cause relies heavily on data from the atomic bomb survivors,
who were exposed more to gamma rays, which are like high-energy X-rays.
But it turns out the lower energy X-rays used in mammography are even worse,"
approximately four times more effective
in causing mutational damage than higher energy X-rays.
And since current radiation risk estimates
are based on the effects of gamma rays,
this implies that the risks of radiation-induced breast cancers
from mammography X-rays is 4 times worse than previously estimated.
But even if that were true, the benefit-to-risk ratio
would still favor mammograms,
which is why you see editorials in radiology journals like this:
"Concern about radiation exposure should not prevent
a woman from undergoing life-saving mammography screening."
But "no trial has ever shown an overall mortality benefit
from screening mammography.
Thus if there is a detrimental effect of radiation exposure
from mammography, even a small effect could offset" the benefits.