Tuesday, December 20, 2011

Screening mammography decisions are close calls

A physician reader of AFP submitted the following post.


I read with interest the December 1st Cochrane for Clinicians article by Dr. Joanne Wilkinson, "Effect of Mammography on Breast Cancer Mortality." On the first page of the article in big print is the "Evidence-Based Answer," which gives a SORT "A" recommendation in favor of mammography because of an approximate 15% reduction in mortality from breast cancer attributed to mammography screening. In small print inside are the conclusions from the Cochrane abstract, which note a 30% rate of overdiagnosis and overtreatment. The Cochrane authors write:

This means that for every 2,000 women invited for screening over 10 years, one will have her life prolonged, and 10 healthy women who would not have been diagnosed if there had not been screening will be treated unnecessarily. Furthermore, more than 200 women will experience important psychological distress for many months because of false-positive findings. It is not clear whether screening does more good than harm.

Having read this - I wonder how many women would continue to opt for regular mammography screening if told that only 1 out of every 2,000 will benefit, whereas 10 out of 2,000 will be overtreated (some presumably with mastectomy), and 200 out of 2,000 (10%) will be temporarily overdiagnosed (and subject to important psychological distress for many months) because of a false-positive mammography reading. Given these statistics, observers outside of the medical community might wonder why "primary care physicians should continue to recommend mammography every two years in women 50 to 74 years of age," as the last paragraph of Dr. Wilkinson's commentary states.

As in much that the primary care clinician does, there are pros and cons to any intervention. For patients to give truly informed consent, it is essential for us to convey to them the numerical chance for life-prolonging benefit (1 in 2,000 for women who undergo yearly mammography for a decade) versus the 1 in 10 risk of a falsely positive mammogram report, and the 1 in 200 risk of overtreatment during that 10-year period. For some women who subscribe to the "n of 1" theory, screening mammography may be worth the risk, effort and cost because of the chance that it may save their lives. Others may decide that the odds of experiencing benefit are not in their favor. Shouldn't the choice to undergo mammography be up to the patient?

Ken Grauer, MD
Gainesville, Florida


  1. A one in 2000 chance your life would be spared? That's a no brainer.

    We women have a ten percent chance of getting breast cancer in our lifetime, so the worry is there anyway.

    As for "important psychological distress for months": what, are we women still fragile subhumans who need smelling salts when faced with problems?

    and that part about "months": Where do you practice? Most of my women get referred and the lump diagnosed in a week or two.

  2. Thanks for your comment Boinky. You bring up important points.
    #1) Not all women feel the same about these issues. As a clinician - I was more than happy to order mammograms at whatever frequency my patient desired - as long as it was done with full informed consent. All I am saying is that some women have told me in equally strong terms that if the chance of benefit is only 1 in 2,000 for doing yearly mammograms with much higher risks of not only false positive readings, but of potentially unnecessary surgical procedures - they would opt against yearly mammograms. It's their choice.

    #2) I am among the most positive supporters of women as the equal of men. I've had a fair number of patients (as well as friends) who have undergone tremendously scary periods (sometimes long-lasting) until clarification could be made on their mammography findings. The figures I cite for the number of women affected psychologically are NOT mine - but those of the esteemed investigators of the Cochrane report.

    #3) It is VERY different if a woman has a lump. I'm a firm supporter of immediate surgical consultation (on the phone that day) for clarification of diagnosis. Different story for screening mammography with a normal breast exam ...

    #4) It is well known that with prostate cancer - many of the malignancies are the kind the patient dies "with" but not "of". Increasing evidence suggests the same is true for breast cancer - in that not all such malignancies are necessarily life-threating. Clearly if I was found to have a "breast cancer" - I would immediately have it treated in intensive manner (and not hang around waiting to see if it was the kind that is going to cause problems ... - which is not always evident on initial diagnosis). That said - a look at the numbers I cite above from the Cochrane report at least to me suggest it is not an "open-and-closed case" - such that there are potential downsides to screening.

    #5) My MAIN point = "Different strokes for different folks" - and I just think it should be up to the patient to decide IF they desire screening - and if so with what frequency. As long as I can be sure that their decision is made with full informed consent - I will support it completely.

    #6) Thanks for expressing your views - Ken Grauer, MD