Image via Wikipedia
Or did they? If you listened to the news or read almost anything, that's the impression rabid, frothing at the mouth "journalists" gave. Yes, I'm talking to you, Sanjay Gupta. You're about to get your MD taken away by the IcedLatte Medical Excommunication Squad. You're an obnoxious little twerp and spouting nonsense from your bully pulpit about which apparently you know nothing is getting on my last nerve.
Prevention and screening are so lovely and warm to think about. You go in to see your doctor for your (almost always useless for detecting disease) annual physical and leave with a prescription for your mammogram and a referral for a colonscopy, and once those are done, you feel great because you know you're cancer-free. Maybe.
A screen is by definition for detecting a disease in an asymptomatic patient. When I order any screening test, I think about:
- What is the prevalence in the population of the disease we're testing for? The less the diseases exists, the less the chance in general that a screen will be positive because most people simply don't have it.
- How good is this test? How many people who truly have the disease does it pick up? That is the "sensitivity." How many people with the disease will it miss?
- What are this patient's unique risk factors? For example, in a female who is 45 but still have regular periods with no sign of slowing down, is her breast tissue still going to be really dense making a negative mammogram not very helpful? What if her mother had breast cancer? What if her mother didn't have breast cancer, but a maternal aunt did at 35? Not all 45 year old women are created equal.
- As noted above, there are technical considerations with a test. Mammograms are better screens for some types of breast tissue. A negative test is less reassuring in others.
- What was the exam like? If then exam is negative, and only if it's negative, then I can do a screen. If it is positive, then forget the screen, we're going to do a diagnostic test. Screening guidelines don't have anything to do with that at all.
- What will I do if the screen is negative? If I'm suspicious--but only if the exam is negative--will I believe the test? If not, should I skip the screen and consider a diagnostic test?
These groups look at huge numbers of patients over time and tell me things like "How many mammograms does it take in women 41-49 to save one life from cancer?" Turuns out it's about 2000. That alone isn't a value judgement, it's just a number. One of the variables I plug into whether I should screen or not.
To make matters more complicated, they all rate their evidence and level of certainty about the evidence, in sort of a "Great data and lots of it. Go for it." to "One study with one guy who was half asleep and possibly drunk when he did it. Proceed with caution." I paraphrase, but I think you get my drift.
Last, but certainly not least, like every other physician in the world, I'm always plotting my next move. If you have a mammogram, say, and it's a little positive, what am I going to do? If it's a lot positive, what is my next step? A little positive is a problem. There is increasing evidence that some breast cancers spontaneously regress, perhaps 20%. The screening tests we have right now can't differentiate who exactly is in that cohort who won't go on to develop an invasive cancer. FURTHERMORE, will early detection make a difference? If we pick up a cancer early, does it go without saying that it will make you live longer? As it turns out, not necessarily.
Confused? That's for your doctor and you to talk about, sitting in an exam room. The USPSTF isn't trying to get between you and your mammogram. The recommendations are just trying to clarify some of the variables in the giant screening equation. Their recommendations will change. The screening tests will get better. In the meantime, don't go burning your bra at your nearest mammography suite.
For an excellent discussion in exhaustive but terrific details, check out:
The USPSTF recommendations for breast cancer screening: not the final word (written by a breast cancer surgeon and researcher
Truth squad needed on breast screening quotes from Gary Schwitzer
Screen saver from Slate, written FIVE YEARS AGO about the perils of breast cancer screening
One last thought. Screens cost money. I think about that with regard to you (Do you have insurance? If you do, do you have coverage for preventative services?), but not necessarily with regard to populations. This isn't pretend money, though, it's real money. To save a life in a female between 40-49, it costs (assuming the mammogram is about $150) $300,000. Yes, yes, what price life? But you just got a new job at an insurance company. You must decidie what is covered and what isn't. What are you going to deny--vaccines for sweet little babies? Cancer treatments? Knee replacements? Grandma's small bowel obstruction surgery? If you put the money in one pot, which pot do you take it out of?
![Reblog this post [with Zemanta]](http://img.zemanta.com/reblog_e.png?x-id=8dee4748-0cb4-446e-8d6f-4ef88ceb8eba)



