"Why Mammograms Don’t Appear to Save Lives"
Critics of mammogram breast cancer screening
claim that on a population scale, it’s never been shown to actually
prolong women’s lives on average.
But, look at this clear drop in breast cancer mortality
in the UK right when routine mammograms were introduced.
Same here in Denmark: a nice drop in breast cancer mortality
right after screening started.
That didn’t appear to be the case in Switzerland, though,
where breast cancer mortality was declining
years before routine mammograms were introduced.
Hmm, so let’s go back and look at that UK graph.
It’s tempting to conclude that breast screening
caused the drop,
but it is a little suspicious that
the drop happens immediately.
You’d expect it to take a few years to manifest.
And, if you split it up by age group,
the whole thing falls apart.
Here’s what the graph looks like.
And, this is the only age group
that started screening at the time.
So, there were drops in other age groups too
that weren’t getting mammograms.
Same with the Denmark data.
This is the line for the areas that got screened;
this is the line for the areas that didn’t get screened.
You see the same drop in breast cancer mortality
with or without.
What’s going on?
Here’s the U.S. data.
Looks just like that UK graph,
where there’s this beautiful drop in breast cancer mortality
right when mass mammograms were introduced around 1990,
but check it out: the same drop—in fact even more,
among women getting less screening,
and an even greater drop in breast cancer mortality
among women not getting mammograms at all.
“In other words, there was a larger relative reduction
in [breast cancer] mortality among women
who were not exposed to screening mammography.”
So, what happened?
The decrease in mortality is probably
“largely the result of improved treatment, not screening.”
Breast cancer mortality started dropping
all around the world at about the same time,
regardless of when mammogram screening started.
There was “no relation at all between start of screening
and the reduction in breast cancer mortality.”
The declines “are more likely explained by the introduction
of [the estrogen-blocking drug] tamoxifen.
You can see it really clearly in the U.S. data,
with breast cancer death rates plummeting in the United States
after FDA’s tamoxifen approval in 1990.
Now, this doesn’t mean breast cancer screening
isn’t playing some role,
and in fact, randomized controlled trials have shown that routine mammograms
may reduce breast cancer mortality by 20%.
Now, that 20% drop is from like 5 in a thousand women
dying during that time from breast cancer without screening,
down to 4 in a thousand dying with screening;
and so, when you graph it, it doesn't look that impressive.
The red line is the risk of dying for women
that are invited for routine screening,
and the green line is the risk of dying for women
not getting mammograms.
They’re practically right on top of one another,
and this is assuming mammograms don’t increase deaths
from other causes.
If we take into account the cardiac and lung cancer deaths
caused by radiation treatments in women
overdiagnosed with pseudodisease
and treated for cancer unnecessarily thanks to mammography—
there doesn’t appear to be any overall mortality benefit.
Why aren’t mammograms more effective?
It seems so simple: catch the disease early, right?
It turns out, by the time
breast cancer is caught by mammogram,
it may have already been growing for literally decades.
“It is, therefore, misleading to say
that breast cancers are caught ‘early’ with screening.”
They may actually be caught very late.
Without mammograms, breast cancer may not be caught
for 22.8 years,
but with mammograms, breast cancer may only grow and spread
for 21.4 years.
No wonder mammograms don’t do a better job
at preventing breast cancer deaths,
if the cancer can spread before you can cut it out.
Concerns have even been raised that the trauma from surgery
may accelerate the growth of any cancer left behind,
and maybe that would help explain
why there’s not more benefit to screening.
Regardless, 9 out of 10 women may still be in the dark,
overestimating the mortality reduction from mammography screening
by like an order of magnitude, 10-fold or more.
About the same percentage of men
thought the same thing about prostate cancer screening,
vastly overestimating the benefits or simply not knowing.
Only 1.5% of women surveyed were in the ballpark.
Ironically, those reporting frequently consulting with their physicians
and reading health pamphlets did even worse,
overestimated the benefits even more,
raising a question that was asked decades ago
by a director of a mammogram project, as she lay on her death bed
before succumbing to breast cancer herself.
Realizing even back then, routine mammograms
may not actually be saving women’s lives,
she asked: “Are we brainwashing ourselves
into thinking that we are making a dramatic impact
on a serious disease before we brainwash the public?”