MAMMOGRAPHY DEBATE CONTINUES

Older randomized trials found that screening mammograms reduced breast cancer mortality, but they were conducted during the pre-tamoxifen era when treatment of breast cancer was less effective.

In 1980, Canadian investigators began a randomized trial of mammography and physical examination in almost 90,000 women aged 40-59 years, and they now report findings based on up to 25 years of follow-up. ^[1] Each woman underwent an initial clinical breast exam and then was randomly assigned either to 5 annual mammograms or to no mammography.

The mean size of cancers diagnosed in the women undergoing mammography was 1.9 cm, significantly smaller than the mean of 2.1 cm in the no-mammogram group. However, the proportion of tumors that were node positive was similar in the 2 groups.

The 25-year cumulative mortality from breast cancer was almost identical among women in the mammography and no-mammography arms; these findings did not vary by age group.

With 15 years of follow-up, 666 cases of breast cancer were detected in the mammogram arm and 524 in the no-mammogram arm. The excess 142 cases of breast cancer in the mammography group represents overdiagnosis of tumors destined not to cause future problems.

This study's findings on lack of efficacy of screening mammograms and overdiagnosis parallel those of other recent studies. ^[2-5] Screening mammograms are costly and are associated with high rates of false-positive findings.

For decades, we have all marched to the drumbeat of "mammograms save lives." Annual screening has become for us an easy recommendation to make, whereas for our patients, the reassurance that accompanies a normal mammogram is comforting.

With this new information, counseling our patients about the low efficacy and overdiagnosis associated with screening mammograms takes time. Many patients will be perplexed by this information; others may view it with suspicion.

While we await updated guidance from professional societies, my approach is to encourage patients to follow the 2009 US Preventive Services Task Force guidelines: Start at age 50 in average-risk women and screen every 2 years. ^[6]