The Case against Mammograms
As improbable as it sounds, studies have suggested that about a quarter of screening-detected cancers might have gone away on their own. For an individual woman in her 50s, then, annual mammograms may catch breast cancer, but they reduce the risk of dying of the disease over the next 10 years by only .07 percentage points — from .53 percent to .46 percent. Reductions for women in their 40s are even smaller, from .35 percent to .3 percent.
If screening’s benefits have been overstated, its potential harms are little discussed. According to a survey of randomized clinical trials involving 600,000 women around the world, for every 2,000 women screened annually over 10 years, one life is prolonged but 10 healthy women are given diagnoses of breast cancer and unnecessarily treated, often with therapies that themselves have life-threatening side effects. (Tamoxifen, for instance, carries small risks of stroke, blood clots and uterine cancer; radiation and chemotherapy weaken the heart; surgery, of course, has its hazards.)
See Peggy Orenstein in the NYT Magazine.
This is a classic example of the trade off between Type I errors (false positive: diagnosing cancer when none exists) and Type II errors (false negative: diagnosing cancer free under the presence of cancer). This is an excerpt from the European Journal of Cancer:
“When analysing a single-arm phase-II trial, based on a design with a pre-specified null hypothesis, a 5% absolute error in the expected response rate leads to a false positive rate of about 30% when it is supposed to be 10%. This inflation of type-I error varies only slightly according to the hypotheses of the initial design.”
http://www.ejcancer.com/article/S0959-8049(11)00175-4/abstract
Isn’t this just a gambling problem? We are betting that the money we win (the dollars and lives saved associated with early detection) is greater than the money we lose (the costs of the mammogram plus the cost of unnecessary treatment if the mammogram shows something that isn’t there).
I’ll take the casino table instead. There I can at least see where my money is.
Reading this article reminds me of the time when I was reading about the article on how doctors die, or how they choose to die.
Although I understand the economic reasoning behind your statement, but I feel like when it comes to health, people don’t like to take risks, certainly not with breast cancer, no matter what the number counts are!
It is no surprise that there is over-treatment in this area. Doctors in this country are incredibly quick to test you and treat you without doing their own research first…usually in fear they may get malpractice lawsuits and/or convenience.
I agree with Samuel. Not much is new here in terms of over-treatment.
Well, I think doctors are being cautious in this instance. Let’s remember that medical schools (vast majority) hardly give any research preparation to doctors. Therefore, they operate under reliance of scientists and when these results aren’t as conclusive, they’ll continue to keep treating in order to not take “any risks.”
Yeah, since we are dealing with cancer here, I think people would continue to ignore this in order not to take absolutely any risks. Hopefully further research can provide more clearance on this.
Women who don’t have breast cancer (and are not at super high risk for it due to BRCA genetics or some other known risk factor), are treated for it without knowing whether they have it? Really?
They are prescribed tamoxifen (note the lower case as it isn’t a trade name)?
Usually the unnecessary treatment that people lobbying for cost control and higher type II errors (as Gabriel Odom points out) consists of biopsies or extra imaging.
If women’s health care is really this corrupt, it would seem that a little investigative muckraking might well earn this reporter a Pulitzer Prize.
Linda, I’ll be looking forward to this article 🙂