Risks of Mammography

Last week, I presented the U.S Services Task Force’s (USPSTF)recent revision on its mammography guideline.  I agreed with the assertion that lives will be saved.  There is a little more to the story.  When a task force or an organization is devising a preventive medicine guideline, lives are not the only consideration.  

First, mammography is a screening test – an exam performed on an individual without symptoms to prevent illness.  For clarification, a mammogram, unlike screening colonoscopies, is not designed to prevent cancer.  The objective is to detect breast cancer at an early phase which should result in a more favorable prognosis.

Whenever a screening test’s target population is widened, as just occurred with USPSTF’s mammography revision, more lives will be saved.  For example, if we started performing screening colonoscopies at age 30, of course we would save lives since colon cancer can arise in folks in their 30’s.  However, what are the costs and risks of such an aggressive approach?  Medical experts have determined that the societal benefits of colon cancer screening at age 30 are insufficient to recommend the practice, even though some lives would be saved.  (Obviously, an individual who is found to have colon cancer at age 35 might have a different view of the issue, but medical policy should not be based on anecdotal events.)

Similarly, if we lowered the speed limit on all federal highways to 35 miles per hour, lives would surely be saved, but society has opted to accept relatively rare highway catastrophes to serve the greater good.

The point is that medical guidelines are not designed to save everyone.

Should this be the new federal highway speed limit?

At what age should a preventive screening test start?  There is no definite sweet spot.  Experts debate this very issue with each screening test and struggle to achieve a consensus.  Think of my speed limit example.  What should the speed limit be?  50 mph?  65 mph? What costs and inconvenience is society willing to bear to reduce traffic fatalities?   Same with mammography and the new expanded guideline.  How many additional women saved would be worth the false negative results, false positive results, breast biopsies and excision of innocent lesions, anxiety for patients and their families who must wait on further testing and results, treatment of breast cancers that may have remained dormant for life, complications and side effects from overtreatment, general medical anxiety from the experience and the consumption of medical resources? 

Mammography benefits have been demonstrated on studies of large numbers of women.  However, the benefit that an individual woman can expect is likely less than you would think.  Ask your doctor to explain this paradox to you.  If patients understood this critical point, their knowledge of medical testing and treatment would be transformed.

Of course, every life matters.  I’m a physician who has dedicated my professional life to this mission.  But those who are charged with creating population guidelines have more than just lives to consider. They strive to balance many competing factors in a utilitarian manner knowing that some of us will be left out. 

Women who are counseled to undergo mammography should know both the benefits and the risk of harm.  And I argue forcefully that it’s better to have this conversation in advance before the test has been ordered..