20 October 2015

Medicin-y.

"A woman’s lifetime risk of dying from breast cancer is 2.7 percent without screening. Kerlikowske calculates that a woman who follows the new USPSTF guidelines could drop that risk to 2.0 percent, and one who follows the ACS guidelines may reduce the risk a few decimal places more, to between 1.8 and 1.9 percent. To get these benefits, the USPSTF program requires 13 total mammograms in a woman’s lifetime, and the ACS regimen will result in 20 breast X-rays.

In exchange for these risk reductions, 61 percent of women who have annual mammograms and 42 percent of women who have biennial mammograms will be called back at least once for follow-up tests that reveal they do not have cancer, researchers write in an accompanying paper. The anxiety and stress of such a false alarm is the most common harm, but it’s not the only one.

In its own analysis, the USPSTF calculated that if 1,000 women follow its advice and have a mammogram every other year from age 50 to 74, 146 of them will be subjected to unnecessary breast biopsies and 18 of the 1,000 will be diagnosed and treated for a cancer that would have never harmed them (a problem called overdiagnosis and overtreatment). Women who have mammograms more often, as they would under the ACS guidelines, will experience more of these downsides."

- Notice this is roughly the number of women who are dying of breast cancer at all with this regimen. And the unnecessary treatment rate is way more than the number that are being treated successfully to avoid lethal developments. All of that treatment comes with its own complications and issues, and stress and fear associated with possible diagnosis (even before considering the enormous financial costs it burdens us with to deal with all these unnecessary procedures).

What does this mean "scientifically"?
- We need much better detection methods. Mammograms appear to be little better than junk science as they have way too high of a false positive rate and way too small of a detection rate. It's possible this is a problem of there being a fairly small risk, but the lifetime risk here is significant enough that we should be doing something. This feels a lot like a "this is something" solution rather than a very useful one. You might as well flip a coin if it's close to 50% false positive rates to decide whether your doctor thinks you might have something that needs checked out.

This is often over 50%. A coin flip might be a better option. The author's decision to just forgo them entirely may be the wiser course in the meantime. (I personally like Austria's recommendation of "whatever").

- It might also be that doctors don't have any idea how to use them, or more likely use the data they get in order to help patients making informed decisions about their care and health. This is a widespread problem in medicine and it likely encourages over use of procedures and treatment, particularly of scary things like cancer. Cancer is scary. Thinking you have it, or could get it, is scary. Therefore, as much medical treatment to prevent it as we can afford is what most people think is reasonable in response. This is not actually reasonable as a response to the actual risks of cancer that most women will be afflicted with. Doctors should have a better idea how to discuss this problem sensibly. Also they may need to have some incentive to do so. The incentive right now appears to be closer to "generate breast cancer patients" rather than "prevent/detect/treat actual breast cancer when it appears in my patients".

- Looks a little better at detection relative to false positives after age 50 (not into the "good at it" rates, but significantly better than what we do now). This is essentially when the rest of the developed world even starts bothering with these questions. What might be one reason why they delay is it reduces the excess costs of unnecessary treatment without significantly reducing the number of women who are put at risk (possibly 1/1000).

More comprehensive studies have pointed out that this does not account for the number of women dying of any cancer total. Which is effectively unchanged by mammograms or no mammograms. All the focus on breast cancer may be obscuring other cancers that need to be attended to for the health of women (cervical cancer for instance has similar problems with our current detection regimen).

Or it maybe obscured here because our actual treatment options are quite poor.

- The biggest problem here is that threads in response to these changes in guidelines are inherently based upon anecdotal evidence. "I found a lump and I was 32" is treated as a data point against changing the current system. There are potentially higher risk factors as well (genetics for example). Patients don't really understand these, usually (many women will, but not everyone on an open comment thread does). Doctors might, or at least should, and can screen based upon them. Usually the recommendations allow for these deviations. The political economy problem is that many people will then worry if insurers will pay for it if it is "not recommended".
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