October 30, 2012
Breast cancer screening of women over 50 saves lives, but leads to overtreatment of many more women, an expert group says. For every life saved, the group says, 3 women will be treated for cancers that never would have harmed them. The United Kingdom's health department and Cancer Research U.K. sponsored the study. The expert panel added together the numbers from 11 prior studies. They concluded that screening of women in their 50s reduces breast cancer deaths by 20%. They looked more closely at 3 studies that randomly divided women into 2 groups. One group was invited to regular screening, and the other group was not. Based on these studies and other information, the expert group estimated overtreatment rates. In the UK, women over 50 are invited to have screening mammograms every 3 years. The panel concluded that about 0.43% of these women will be saved from dying of breast cancer. Another 1.29% will likely be treated for cancers that would not threaten their lives. The journal Lancet published the study. The Associated Press wrote about it October 30.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
Women have to deal with mixed messages about screening mammograms for early detection of breast cancer.
The U.S. Preventive Services Task Force (USPSTF) publishes advice about health screening and disease prevention. The advice is based on evidence evaluated by experts from different specialties. Therefore it is less likely to have a bias.
Regarding breast cancer screening, the task force recommends:
The American Cancer Society (ACS) and other well respected medical groups vehemently disagree. They say the USPSTF guidelines will miss too many early cancers, and that this could cost lives. The ACS recommends a mammogram every year starting at age 40 for women at average breast cancer risk. The ACS also recommends a yearly clinical breast exam.
Some experts disagree with both groups. They say there is not enough evidence to support widespread breast cancer screening with mammograms for anyone. They cite other research to support this view. These studies suggest that screening mammography finds too many cancers that don't require treatment because they would not shorten a woman's life. These experts say that better treatment, not routine mammography, has led to increased breast cancer survival.
Now an expert panel from the United Kingdom has weighed in. This group carefully evaluated the results of 11 clinical trials. These studies looked specifically at how many lives are saved each year by screening mammograms compared to the number of women treated for breast cancers that would not have shortened their lives. The British experts concluded that breast cancer screening saves lives. But they said for every woman saved from a breast cancer death, 3 women receive breast cancer treatment they did not need.
The other major problem with mammograms is the large number of false positives. A false positive mammogram is one that shows a suspicious spot that turns out not to be a cancer. But this can't be known until more tests are done. This often includes a biopsy. The British expert panel did not look at false positive mammograms.
What Changes Can I Make Now?
For women at average risk for breast cancer, I will continue to follow the guidelines proposed by the USPSTF. However, if a woman wanted to start yearly mammography at age 40, I would completely accept this decision. I would inform her that it is very likely she will have a false positive mammogram at some time during her life. This could lead to a biopsy and potentially even surgery that might not have been needed.
The problem is that doctors cannot predict what early breast cancers are likely to do. Also, "watchful waiting" is not an accepted strategy for breast cancer.
Mammograms detect early cancer. They do not prevent cancer. But there are some things you can do to help lower your breast cancer risk:
What Can I Expect Looking to the Future?
All the experts are looking at the same evidence. What differs is how they interpret it. So don't expect to see a consensus on breast cancer screening with mammograms any time soon.
What each woman wants to do about screening when she reaches age 40 is personal. If you are at higher than average risk, you will likely want to start screening right away. The balance of risks and benefits of screening mammography between ages 40 and 49 is not clear. So if you are at average risk, you may want to wait until age 50. If you choose to be screened in your 40s, realize that you will likely have a false positive mammogram at some point. If you do have breast cancer, surgery may save your life, or it might be a procedure you didn't really need.