Chance News 67

More fuel for the controversy over mammograms

Mammogram Benefit Seen for Women in Their 40s, Gina Kolata, The New York Times, September 29, 2010.

One of the most contentious debates in medicine is whether mammograms are beneficial to women between 40 and 50 years old. Earlier commentaries about this controversy appear in Chance News 8, Chance News 12, Chance News 14, Chance News 47, Chance News 58, and Chance News 59.

The first sentence in the latest article about mammography makes a bold claim...

Researchers reported Wednesday that mammograms can cut the breast cancer death rate by 26 percent for women in their 40s.

...and the second sentence contradicts this claim.

But their results were greeted with skepticism by some experts who say they may have overestimated the benefit.

The data set on which these bold claims were based is quite good.

The new study took advantage of circumstances in Sweden, where since 1986 some counties have offered mammograms to women in their 40s and others have not, according to the lead author, Hakan Jonsson, professor of cancer epidemiology at Umea University in Sweden. The researchers compared breast cancer deaths in women who had a breast cancer diagnosis in counties that had screening with deaths in counties that did not. The rate was 26 percent lower in counties with screening.

Why the skepticism?

Other experts were not convinced. One problem, said Dr. Peter C. Gotzsche of the Nordic Cochrane Center in Copenhagen, a nonprofit group that reviews health care research, is that the investigators counted the number of women who received a diagnosis of breast cancer and also died of it. They did not compare the broader breast cancer death rates in the counties.

A prominent statistician, Donald Berry, is also quoted in this article.

Questions

1. The research design in the current study was not randomized. Is this an issue?

2. What are the barriers to conducting a randomized trial for mammography?