Green light on mammography, amber on tamoxifen

   In covering controversies about breast cancer, the US media show bias in favour of screening, but are less enthusiastic about chemoprevention, a study has shown.

Researchers looked at how US newspapers and television covered two storiesone about the detection of breast cancer by mammography and the other about chemoprevention by tamoxifenand found striking differences.

In January 1997 a National Institutes of Health consensus panel said that evidence did not support screening for women in their 40s and told women to decide for themselves whether or not to have the test. In March 1997, under political pressure, the National Cancer Institute changed course and recommended screening.

The tamoxifen story broke in 1998, when the National Cancer Institute stopped a randomised trial of tamoxifen versus placebo in high risk women, concluding that tamoxifen significantly reduced the incidence of breast cancer.

Media coverage portrayed mammography as the right thing to do. "The harm of over-diagnosis wasn't stressed. The harm of a medicine, tamoxifen, was seen as clearer," says Lisa Schwartz, one of the study's authors. Tamoxifen stories mentioned the risk of uterine cancer, but often ignored pulmonary embolism.

Schwartz and co-author Steve Woloshin's study, which appears in this week's issue of the Journal of the American Medical Association (2002;287:3136-42)[Abstract/Free Full Text], sought to look at how the media convey health information. "How do you present information to patients to make a decision?" says Dr Woloshin.

Mammography stories quoted members of the consensus panel, government health officials, radiologists, politicians, patient advocates, and members of the American Cancer Society, which supported mammography. Only once did a story quote the US Preventive Services Task Force, which did not recommend mammography for women in their 40s.

Headlineswhich are written by an editor, not the reportershowed a desire for authoritative recommendations ("Why do we play Russian roulette with our lives?"), frustration about uncertainty ("New mammogram report leaves women adrift"), and criticism of the consensus panel ("Stand on mammograms greeted by outrage"). When the National Cancer Institute came out in favour of mammography, articles recommended that women in their 40s have mammograms, although there was no new data.

Tamoxifen articles said women would have to weigh the risks and benefits themselves. Stories quoted investigators in the tamoxifen study, academics, and women taking part in the trial, but there were no quotes from politicians and only three quotes from breast cancer advocacy groups.

Oddly, women were being advised to rely on expert opinion about having a mammogram but to decide for themselves about taking tamoxifen. In other words, they were treated as children in one situation and as adults in the other.

One possible explanation for the difference in press coverage is that the mammography story was about discarding an established medical practice while the tamoxifen one was about adding a new intervention. Peopleand reportersmay be less aware of the negative aspects of screening than negative aspects of drugs.

Schwartz and Woloshinwho are affiliated with the Veterans Administration Outcomes Group in White River Junction, Vermont, and Dartmouth Medical School, Hanover, New Hampshiresay full information should be provided to patients and emotion should be kept out of the discussion.

At the beginning of this year, a committee of cancer experts triggered a major media debate in the US when they said there was insufficient evidence to show that mammograms prevented breast cancer deaths (BMJ 2002;324:432)[Free Full Text].

Janice Hopkins Tanne, medical journalist. 

New York