
MRIs can better detect cancer in women with dense breasts, study finds - catoc
https://www.nytimes.com/2019/11/27/health/dense-breasts-MRI-cancer.html
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azalemeth
Breast cancer screening is one of those things where there is a serious risk
of overdiagnosis and iatrogenic injury and one has to seriously think about
how many such injuries are acceptable per life saved.

I personally think that the targeted use of MR -- which, with contrast, has
its own (minute, marginal) risks (broadly comparable to mammography) is
appropriate, as the image quality really is an order of magnitude better than
plain film alone.

Nevertheless, this rate of iatrogenic harm has to be considered -- heck, just
from basic Bayesian probability, you'll know that any imperfect test for a
rare disease results in a lot of false positives.

Here in the UK, it's generally accepted that the ultimate rate of 'harm', that
is, over-treatment, is about 3:1; "that is one breast cancer death prevented
for about every three overdiagnosed cases identified and treated". Both the
NHS and most women feel that, knowing this, "accepting the offer of breast
screening is worthwhile" \-- and I personally agree with them. [both 1]

\---

[1]
[https://www.thelancet.com/journals/lancet/article/PIIS0140-6...](https://www.thelancet.com/journals/lancet/article/PIIS0140-6736\(12\)61611-0/fulltext)

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caycep
The argument for increased iatrogenic injury is always brought up with new
technologies (and sometimes used to dismiss their use). In this case,
presumably, you mean increased amounts of invasive biopsies w/ potential
complications, bleeding, pain, etc. Esp with false positives.

The converse thought is, with the increased resolution, image quality and
addition of a 3rd dimension over plain film mammographies, how much reduction
in false positives iatrogenic can one reasonably expect?

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ska
The situation is a bit more nuanced than you suggest. MRI gives you 3D
information and better tissue contrast, but much worse resolution. This makes
things difficult with micro-calcifications, but really helps with some lesions
in dense breasts.

The best specific information comes with a contrast agent, but that's not
appropriate for screening for the iatrogenic reasons you mention, but is
suited to diagnostic followup.

Worth noting on a big enough screening population, biopsy complications
include death by infection, etc. You also have to consider the opportunity
cost of the machinery and tech time, etc. So while sometimes approaches are
dismissed for this (e.g. contrast agents for screening) it is not done without
though.

As an overall health system, too, you really have to evaluate the systemic
costs and opportunity costs, particularly with a screening program. Two big
variables here are the infrastructure & workflow costs for introducing MRI
mammo into a screening program (those machine and tech hours come from some
other worthy use) and radiologist attention. Breast screening already
struggles with allowing enough time for careful review of 2D data sets, adding
more information of a 3D set (potentially additionally!) means you may have to
trade off increased cost/time (or reduced coverage) against FN count.

So that's the tip of that particular iceberg. It's not easy, and a lot of
smart people have been thinking about this since the 90s.

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1e-9
An interval cancer is one that is diagnosed outside of the regularly-scheduled
screening exams.

Example: A woman feels a lump, goes to see her doctor immediately rather than
wait until her next scheduled screening, and this results in a cancer
diagnosis.

One of the main reasons this happens is because the previous regular screening
exam failed to detect the cancer.

Mammography misses cancers more often in dense breasts than in typical
breasts. MRI has long been known to be much more sensitive than mammography at
finding cancer in dense breasts.

This study looked at whether adding an MRI to a screening mammogram for
extremely dense breasts would result in fewer interval cancers. It did, which
is not surprising, but this was a relatively small study that resulted in only
4 cancers diagnosed in women who actually underwent the supplemental MRI.

Link to the paper:
[https://www.nejm.org/doi/full/10.1056/NEJMoa1903986](https://www.nejm.org/doi/full/10.1056/NEJMoa1903986)

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always_swapping
Don’t want false positives? Organ-specific positron emission tomography for
mammography. Malignancies light right up.

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markus92
PET isn’t really suited for a screening population due to relatively low
availability and high cost (esp. compared to a mammography). Resolution is
also bad and it tends to also light up inflammations. So it probably wouldn’t
help too much for reducing false positives.

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always_swapping
In the case of patients with dense breasts, which in the article undergo MRI,
an argument can be made for PET in both availability and cost now that these
patients are in MRI territory. Also, organ-specific PET is working on the
resolution problem but I'd agree that if you were to put a patient into a run
of the mill PET scanner there wouldn't be much clinical usefulness.

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zrail
It’s unclear to me how screening reduces cancer. That said, this additional
screening with MRI seems like it may reliably detect cancers earlier in the
population of women with dense breast tissue, who are more likely to develop
cancer in the first place. Earlier detection generally results in better
outcomes.

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war1025
Based on a quick look around the web, "interval cancer" means specifically a
cancer that develops after having previously received a cancer screen where no
cancer or pre-cancer was found.

So basically it reduces "interval cancer", not "cancer", by more effectively
finding warning signs.

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brunoTbear
I’m heartened to see more aggressive screening protocols be studied. Fear of
iatrogenic harms seem to cloud our progress towards early treatment.

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TaupeRanger
Fear of iatrogenic harms is well founded and important. It doesn't look like
you even tried to argue otherwise - you just implied that aggressive screening
is worth the risk. This is silly and harmful, especially considering cancer
screening has never been shown to save lives:
[https://www.bmj.com/content/352/bmj.h6080](https://www.bmj.com/content/352/bmj.h6080)

