The Women's Health Resource. On the web since 1997.

Medical Experts Refute Recent Study that Criticizes Mammography (dateline January 7, 2000)


A recent study by Danish researchers published in the January 8, 2000 issue of The Lancet has led medical experts to reiterate the benefits of screening mammography . The widely publicized study claims that mammography does not reduce the mortality rate of breast cancer and is therefore useless as a screening tool. Several organizations including the American Cancer Society (ACS) and Britain’s Department of Health call the Danish findings inaccurate and unjustified. Researchers in the United States and Britain argue that mammography vastly improves breast cancer diagnosis and prognosis (expected outcome).

Screening mammography plays a key role in detecting breast cancer at an early stage, when it is most curable . Screening mammography is an x-ray examination of the breasts performed on women who are asymptomatic (have no symptoms of breast cancer). In the early 1980s when only 13% of American women regularly received mammograms, the average size of breast tumors was 3.2 centimeters (equivalent to one and one-fourth inch). By the late 1990s, 60% of American women received screening mammograms and the average size of breast tumors was reduced to 2.0 centimeters, verifying that screening mammography significantly improves breast cancer detection. Also, in most breast cancer cases diagnosed today, the cancer has not yet spread to the lymph nodes, said Harmon Eyre, MD, chief medical officer for the American Cancer Society (ACS). The death rate from breast cancer has been falling steadily for the past 10 years, in part because of mammography, said Eyre.

The Danish researchers analyzed eight mammography screenings, the majority of which were conducted in Europe. Each original study revealed that screening mammography decreases the breast cancer mortality rate. The Danish researchers argued that the studies had not sufficiently randomized the participants, thereby compromising the results. However, ACS pointed out that two of the trials the Danish researchers analyzed had already been under attack for their randomization methods. Even when the results of these trials were re-analyzed, the findings still revealed the benefit of mammography in helping to detect breast cancer at an early stage, said Robert Smith, PhD, director of breast cancer screening for ACS.

Officials in Britain also criticized the Danish study, arguing that screening mammography has detected more than 8,000 breast cancers between 1997 and 1998 alone. Britain’s Department of Health noted a 14% decline in the number of deaths from breast cancer between 1989 and 1998. Muir Grey, MD, head of Britain’s National Health Service, feared that the amount of attention the Danish study has generated may wrongly convince women that mammograms are not necessary.

In the United States, the Center for Disease Control and Prevention estimates that screening with mammography has the potential to prevent 15% to 30% of deaths from breast cancer among women over 40 years of age. Since the risk of breast cancer increases with age, all women 40 years of age and older should have annual mammograms in addition to yearly clinical breast examinations and monthly breast self-examinations . Younger women at a very high risk of breast cancer (such as those have tested positive for mutations of the BRCA1and BRCA2 breast cancer genes) should speak with their physician about beginning annual mammograms as early as age 25. To date, mammography is the most accurate breast cancer screening tool and the only screening exam to be approved by the U.S. Food and Drug Administration (FDA).

Additional Resources and References