Here we go again….the use of screening mammograms up for debate. Some recent studies make this contraversial issue…well, more controversial.
Researchers in Canada studied more than 90,000 women for 25 years and found that women aged 45-59 who received mammograms every year for 5 years were no less likely to die of breast cancer than women who did not get regular screening. Women aged 50-59 in the study had a yearly physical exam. Also, 22% of women with screen-detected invasive breast cancer got treatment that they really didn’t need. Both groups of women in the study when diagnosed had excellent treatment and shared the same life-saving opportunity for treatment. There were 500 deaths from breast cancer in the mammography group and 505 among those without screening.
Then there is another study conducted at 2 Boston hospitals that looked at mammography history and cause of death in women who were diagnosed with invasive breast cancer between 1990 and 1999. These were primarily women in their 40’s. Among 609 deaths from confirmed breast cancer, 29% occurred in women who had been screened and 71% occurred in unscreened women. The median age of women who died of breast cancer was 49 verses other causes in which the median age was 72. Only 6% of women diagnosed had gotten a mammogram more than 2 years from the previous one. Whereas, 65% of the women diagnosed had never been screened.
Even though this Boston study would indicate that regular screening in women younger than 50 would lower mortality from breast cancer, there are other things to consider. This study was conducted in women already diagnosed with breast cancer and we don’t have a comparison of the outcome of women screened or not screened. What kind of treatment was provided by screened and unscreened women? Demographically, those women who were screened infrequently (or never) are considerably less affluent and less educated than those who receive regular screening. Less screened women are also less likely to seek medical attention in a timely manner upon finding a palpable breast mass. This would lead to differences in breast cancer outcomes independent of screening history.
The main concern is over-diagnosis. When a mammogram detects an irregularity, theres a natural urge to treat it. This results in unnecessary surgery and toxic treatments (chemo, radiation, hormone drugs) that can do more harm than good. Also, in reference to the canadian study, breast cancer treatments have improved so much that the outcomes of average risk patients diagnosed at an earlier stage (due to mammogram) as well as those diagnosed later (lack of screening) are similar.
The U.S. Preventive Services Task Force in 2009 made recommendations that screening begin at age 50 for women and continue biennially until age 74. Of course women at higher risk starting at age 40 could be screened sooner. Many practitioners and major cancer organizations, including the American Cancer Society, felt this was such a major shift in thinking and continues to recommend yearly screening at age 40.
The bottom line: Until cancer researchers can find ways to identify those subsets of women at higher risk due to genetic susceptibility who could benefit from early detection and treatment, individualized recommendations for each woman is crucial.
Reference: Kaunitz, A. “Does Screening Mammography Save Lives?” NEJM Journal Watch: Women’s Health. Vol. 18, No. 10. P. 74.
Kolata, G. “Vast Study Casts Doubt on Value of Mammograms”. The New York Times-health. Feb. 11, 2014.