November 19, 2009
The Mammogram Conundrum
Posted by Christine Hurt

Anyone who is interested in behavioral psychology has to be fascinated by the consequences of The United States Preventive Services Task Force reporting this week that women should not get annual mammograms until age 50, instead of its earlier recommendation of age 40.  I turned 40 last December and so have had one test; I feel a little like my sister did when Texas raised the drinking age from 18 to 21 when she was 19.

The Task Force reports that cost-benefit analysis dictate less screening for women age 40-50 because the modest benefits are outweighed by the harms of false positives, which result in anxiety and further testing.  The report states that mammograms save 1 in 1,904 women in the 40-50 age group and 1 in 1,339 women in the 50-59 age group.  From the report:

The 6 models produced consistent rankings of screening strategies. Screening biennially maintained an average of 81% (range across strategies and models, 67% to 99%) of the benefit of annual screening with almost half the number of false-positive results. Screening biennially from ages 50 to 69 years achieved a median 16.5% (range, 15% to 23%) reduction in breast cancer deaths versus no screening. Initiating biennial screening at age 40 years (vs. 50 years) reduced mortality by an additional 3% (range, 1% to 6%), consumed more resources, and yielded more false-positive results. Biennial screening after age 69 years yielded some additional mortality reduction in all models, but overdiagnosis increased most substantially at older ages.

Cost-benefit analysis necessarily puts monetary values on intanglible benefits, but I do wonder what the cost value for anxiety is.  The Task Force may have simply considered the costs of additional testing, but it seems to emphasize the unnecessary anxiety as well.  From what I hear from my friends, the report has created a lot of anxiety!  Women are now anxious that they will be living with undetected cancer.  That has to be put into the equation as well, I guess.

So much that we are told in the way of cancer prevention is reversed periodically, as this op-ed by Gail Collins points out.  Should women believe that mammograms are now not necessary?  Should they wait another few years to see if the Task Force reverses itself again?  This part of the report, which explains the choice of modeling as a methodology, makes me wonder:

Randomized trials of mammography (2–4) have demonstrated reduc-tions in breast cancer mortality associated with screening from ages 50 to 74 years.Trial results for women aged 40 to 49 years and women aged 74 years or older were not conclusive, and the trials (4, 5) had some problems with design, conduct, and interpretation. However, it is not feasible to conduct additional trials to get more precise estimates of the mortality benefits from extending screening to women younger than 50 years or older than 74 years or to test different screening schedules.

I will leave it to the real scientists to discuss the modeling methodology.

And some are skeptical that this government-appointed Task Force is already rationing health care in case the government becomes the primary purchaser of health care.

Of course, anecdote doesn't help scientific proof, but it does enter into how much anxiety this reversal causes.  Women who knew someone that caught cancer early with a mammogram thinks the report is bad.  Women who knew someone who died from cancer that went undetected with mammograms simply shrugs.  No one likes to get a mammogram, but it's not horrible.  Women are generally risk-averse and used to going to see doctors on an annual basis, so they generally do what experts tell them to do to avoid things like cancer, death, etc.  If a Task Force came out and said that colonoscopy was useless, people everywhere would cheer.

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