"Do Mammograms Save Lives?"
What was the impact of the 2009 shift
in recommendations to delay routine screening until age 50?
Ironically, mammography rates of women in their 40s
may have actually gone up.
The thought is that all the media attention
may have just reminded women about it,
underscoring the need to better
translate evidence into practice.
The new recommendations bring the U.S.
closer to European standards:
mammograms every few years starting at age 50.
In 2015, the American Cancer Society
split the difference and recommended
starting at 45 annually
then switching to every other year at 55,
suggesting this would decrease the lifetime risk
of dying from breast cancer
from 2.7% down to under 2%,
based in part on a systematic review
performed by the Cochrane collaboration,
a highly-respected bastion of evidence-based medicine.
The authors of the Cochrane review,
however, wrote in to say they used the wrong number
and that if you look at the studies
they considered were adequately randomized,
there did not appear to be any significant
mortality benefit from mammograms at all,
and that the “data certainly do not support
the popular idea that breast cancer screening saves lives,”
accusing the American Cancer Society
of being more of a political organization
with financial ties to the multi-billion dollar
mammogram industry.
Here’s the Cochrane review they’re talking about,
which concluded that the studies
which provided the most reliable information
evidently showed that screening
did not reduce breast cancer mortality.
If that’s true, then that changes everything.
They concluded that the time has,
therefore, come to re-assess
whether routine mammograms should be
recommended for women of any age,
which is what the Swiss Medical Board did.
They “were struck by how non-obvious it was
that the benefits of mammography screening
outweighed the harms.”
It’s easy to promote mammography screening
when the majority of women believe
that it prevents or reduces the risk
of getting breast cancer and saves many lives
through early detection of aggressive tumors.
I mean, if those beliefs were valid,
they’d be all for it.
Unfortunately, they concluded, they are not,
and so believe that women need to be told so.
From an ethical perspective, a public health program
that does not clearly produce more benefits than harms
is hard to justify.
Their report, not surprisingly, caused an uproar.
Critics argued that the report unsettled women,
but we wonder how to avoid unsettling women,
given the available evidence.
If you ask women what they perceive
to be the benefits of regular mammogram screening,
they think it cuts the risk of dying
from breast cancer in half—
that’s the orange box,
saving the lives of about 1 in 12 women,
but in reality the numbers appear to look like this.
First of all, the risk of dying from breast cancer regardless
is smaller than most women think,
and the reduction in risk—
the differences in the size of the orange boxes,
is much smaller, maybe only 1 in a thousand women benefits.
But hey, doesn’t saving the life
of even 1 in a thousand women make it all worth it?
Imagine if you were in that 1 in a thousand family
whose mom was saved.
But, that may not be true.
One in a thousand women screened
may not die from breast cancer,
but there’s no evidence to suggest
that overall mortality was affected,
which would mean no lives are actually saved.
There's been 10 randomized trials of mammogram screening,
and not one has ever showed an overall mortality benefit.
Wait... How does that make sense?
If mammograms prevent 1 in a thousand women
from dying from breast cancer,
then the only way no lives are saved
is if mammograms ended up somehow leading
to the deaths of 1 in a thousand healthy women,
and that’s preposterous, right?
Let me introduce the concept of over-diagnosis,
the fact that some of the tiny tumors
picked up on mammograms may have never progressed,
or even disappeared on their own;
and so, had they not been picked up,
the women would have been none the wiser
and would have never been affected by it
or even known they had it.
But once you pick up a cancer on a mammogram,
you have to treat it,
since you don’t know what it’s going to do.
But, in some cases, the over-diagnosed cases
where it would never hurt you,
you’re treating the breast cancer unnecessarily.
How common is that, though?
For every life saved by mammography,
as many as two to 10 women are over-diagnosed,
meaning turned into breast cancer patients unnecessarily,
along with all the attendant harms
of chemo, radiation, or surgery without the benefits,
harms can include death.
Imagine being in the family whose mom was killed.
The concern is that unnecessary radiation treatments
may kill as many as are saved;
hence, the no evidence of net mortality benefit.
Radiation treatments to the chest
increase the risk of dying
from heart disease and lung cancer.
Now, those may be acceptable risks
if you actually have breast cancer
that would otherwise kill you.
Treatments that are beneficial for real patients
can be lethal for those who never
should have been treated in the first place.
Even if mammograms don’t save your life,
might they save your breast?
I mean, If you catch a tumor early,
maybe you can avoid a mastectomy?
The opposite may actually be true.
The Cochrane researchers explain that that's why
they published their report.
They thought it was important for women to know
that screening may increase their risk
of losing a breast.
Basically, mammograms have been promoted to the public
with three simple promises
that all appear to be wrong.
Screening does not seem to make the women live longer;
instead it may unnecessarily increase mastectomies.
And, cancers are not caught early;
it may take decades for a tumor
to grow large enough to be picked up on a mammogram.
And, even when they are,
they may not grow any further;
that’s the concern we’re catching too many.
There is so much over-diagnosis
that if a woman really doesn’t want
to become a breast cancer patient,
maybe they should avoid
mammogram screening altogether.
But, if you have breast cancer,
don’t you want to know?
“The small probability that a woman
may avoid a breast cancer death
must be weighed against the more likely scenario
that she may have a false-positive…
or false-negative result…,
or most critically, a diagnosis and treatment of cancer
that would otherwise not have threatened her health
or even come to her attention.”