"Understanding the Mammogram Paradox"
While false-positive results,
pain during the procedure, and radiation exposure
may be among the most frequent harms
associated with mammogram screening,
the most serious downside
is now recognized to be something called over-diagnosis,
so serious as to raise the question,
does it make the whole thing worthless?
The value of doing routine mammograms at all
is being questioned due to over-diagnosis,
which is the diagnosis and treatment of breast cancer
that would never have become a threat
to a woman's health,
or even apparent, during her lifetime.
See, people think that once
you have a cancer cell in your body,
it will progress, predictably and inevitably,
to a terrible death,
and that’s simply not true of most cancers.
Some cancers may outgrow their blood supply,
become starved, and wither away.
Others may be recognized by our immune system
and successfully contained,
and some are simply not that aggressive in the first place,
meaning yeah, it may continue to grow unchecked,
but so slowly that it would be like 200 years
before it was big enough to cause any problems.
And so, in effect, you die
WITH your tumor instead of FROM your tumor.
Indeed, if you do autopsy studies
of young and middle aged women
who just happened to die in a car accident or something,
20% of them had cancer in their breast.
So, like 1 in 5 women
are walking around with breast cancer.
Now, that sounds a lot scarier than it is,
since at that age range,
the risk of dying from breast cancer
is less than 1%.
In fact, your risk of ever dying
from breast cancer in your lifetime
is less than 4%,
which goes to show that many of these cancers
that they found incidentally—
in fact, most of them, would likely have just
fizzled out on their own.
The problem is we continue to have
a 19th century definition of cancer,
dating back, to the 1860s.
See, cancer is defined by what it looks like
under a microscope,
not by what its subsequent behavior is.
So yeah, using that definition,
1 in 5 of these women technically had cancer,
like this 30-year-old here,
but that doesn’t necessarily mean
it would go on and do anything.
The question then becomes:
if it’s so common,
do you even want to know about it?
If it’s going to progress and cause a problem,
then definitely— catching it early
could save your life.
But, if it’s never going to grow,
if it’s going to remain microscopic,
then finding it could actually
be bad for you.
They’d be like, look you have cancer,
we have to treat it—
surgery, chemo, radiation— whatever it takes.
Then, you’d suffer all the physical effects of treatment,
the psychological hell of fearing for your life,
all completely unnecessarily,
if, in fact, it was never going to cause a problem.
That’s over-diagnosis.
These kinds of car accident-type autopsy studies show
that between 7 and 39% of women
ages 40 through 70 are walking around
with tiny breast cancers.
30 to 70% of men older than 60
have prostate cancer,
and up to 100% of older adults
have microscopic cancers in their thyroid glands.
Yet, only point one percent—
1 in a thousand, ends up suffering
or dying from thyroid cancer.
Normally, it just sits there
and doesn’t do anything.
Likewise, even though the majority
of older men may have tiny cancers in their prostates
or a significant number of women in their breasts,
the lifetime risk of death or cancer spread
is only about 4%.
So, if you had a magic wand
that could pick up cancer with 100% accuracy
and waved it in front of people,
your over-diagnosis rate, the probability that
the prostate cancer you’d pick up
would have turned out to be harmless is like 90%,
and nearly every single thyroid cancer,
and a significant proportion of breast cancer cases.
That’s why screening for these cancers
can be tricky, or even potentially dangerous,
since, in many cases— sometimes most cases,
you would have been better off
if they had never found it.
Now, this is not true for all cancers.
There is little evidence of over-diagnosis for
cervical or colorectal cancer, for example.
Those cancers do seem to just keep growing;
and so, the earlier you catch them, the better.
So, institute pap smears
and cervical cancer death rates plummet.
And, just a single sigmoidoscopy
between the ages of 55 and 65
may decrease one’s risk of dying
from colorectal cancer by up to 40%.
Whereas, some studies show
that even getting mammograms every year
don't appear to reduce breast cancer mortality at all.
But, if we assume a 15% drop
and a 30% over-diagnosis rate,
which is what most studies have found,
then that would mean for every 2000 women
invited for mammograms for 10 years,
1 will have her life prolonged
and 10 healthy women would be over-diagnosed.
In other words, they would not
have had a breast cancer diagnosed
if they had skipped screening,
but were instead treated
for breast cancer unnecessarily.
And, about a thousand would have gotten false alarms,
which can be stressful while you wait for the results,
but the harms caused by becoming
a cancer patient unnecessarily can be lifelong
and even mean a shorter life.
It’s important to be aware
that some of the needlessly treated women
will die from that treatment.
For example, radiation treatments
can’t help but penetrate down into the heart as well,
increasing the risk of the #1 killer of women...
heart disease.
This raises questions about doing routine mammograms period,
as it converts thousands of healthy women
into cancer patients unnecessarily,
some of whom may not make it out alive.
Ironically, though, those who do
become mammography’s biggest cheerleaders,
thinking mammograms saved their life.
The mammogram found a cancer
you didn’t even know you had,
and yeah the treatment was rough—
surgery, radiation, drugs,
but it worked, life was saved.
Thank God she got that mammogram;
you should too.
Whereas actually, the more likely scenario—
in fact, maybe the 10 times more likely scenario,
is that the treatment didn’t do anything
since the cancer wouldn’t have hurt you anyway;
so, you went through all that pain and suffering
for nothing.
That’s the crazy thing about mammograms:
the people who are harmed the most
are the ones who claim the greatest benefit.