Mammography Screening – Are the Harms worth the Benefits?

November 16, 2009

By Kate Johnson

As I reported today, decisions about breast cancer screening just got tougher for women in their 40’s with today’s release of new guidelines from the U.S. Preventive Services Taskforce (USPSTF).

Backing off from its previous guidelines (2002), the task force now recommends against annual mammography for normal-risk women in this age-group, where it used to recommend for it. The new recommendation is to have the test every two years instead.

This is a major change from the task force, which is a leader in mammography screening guidelines. It goes against the recommendation of many other major U.S. groups, including the American Cancer Society, which is strongly critical of the USPSTF move.

So, why the disagreement?

It’s a debate over the harms versus the benefits of screening.

There’s growing recognition within the field of breast cancer screening that too much screening can be harmful. The harm is seen in false positive results, which lead to additional imaging and biopsies, and to an overdiagnosis and treatment of lesions that might otherwise have disappeared on their own. “Consistent with the attitude in U.S. medicine that if some is good then more is better, we’ve opted hellbent for more. With no evidence,” Donald A. Berry, Ph,D., told me. As chair of biostatistics at the University of Texas M.D. Anderson Cancer Center in Houston he helped advise the USPSTF on its new recommendations. “This change is overdue.”

But the benefit of routine, annual screening is that it leads to early detection and treatment of lesions that could otherwise be fatal.

For this reason, the American Cancer Society stands by it’s recommendation of annual screening mammography for women in their 40’s – despite the potential for harm. “Surveys of women show that they are aware of these limitations, and also place high value on detecting breast cancer early,” it said in a statement this week.

Dr. Peter Gøtzsche, director of the Nordic Cochrane Centre  and author of several large studies of mammography screening, strongly disagrees with the ACS. “One survey from the U.S. showed that only 8% of women were aware that screening can harm them,” he told me in an e-interview from Copenhagen.

Maybe it has to do with what you define as harm.

The debate over the harms and the benefits of mammography screening will never be resolved, because in the end, it’s a value judgement that is highly subjective.

Some women might be willing to undergo extra tests, and the risks of false positives, and even unnecessary treatment for the peace of mind of knowing they’re getting checked out regularly. I’ve written about high-risk but healthy women who are willing to go to extremes – removing their breasts and ovaries –  for peace of mind. But even normal-risk women worry about breast cancer. For the worrying type, the harms of screening might be worth it, and going home with a clean screen would be the jackpot.