February 12, 2014
News Review From Harvard Medical School -- In Study, Mammograms Don't Reduce Deaths
A long-running study from Canada has added to the debate about the value of screening mammograms. After 25 years, death rates were equal between groups that did and did not get regular mammograms. The study included nearly 90,000 women. Their ages ranged from 40 to 59 when the study began. They were randomly assigned to receive mammograms or not. Those who got the tests received a mammogram each year for 5 years. All of the women 50 and older also received annual breast exams by trained nurses. So did the women in their 40s who got mammograms. The younger no-mammogram group received a single exam at the start of the study. During the next 25 years, 3,250 women in the mammogram group and 3,133 in the no-mammogram group developed breast cancer. About 500 women in each group died of breast cancer. The journal BMJ published the study online. HealthDay News wrote about it February 11.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
Women routinely subject their breasts to the often uncomfortable exam called a mammogram. They endure because they believe it can detect breast cancer at an early stage. And they believe catching cancer early means that it will likely be easier to treat. They believe this will help to save lives.
The American Cancer Society and the American College of Radiology vigorously promote this message to women and their doctors. And most doctors, including me, continue to order routine mammograms.
This study and others have questioned whether screening mammograms save lives. The results of this study suggest they do not.
The authors suggest that breast cancer survival has improved because of better treatments developed during the last 25 years. They note that screening mammograms in many cases find spots that are not invasive cancer. This leads to unnecessary treatment.
Adding to the confusion are the mixed messages women receive. Different specialty groups disagree about the age to begin screening mammograms and how often they should be done.
The U.S. Preventive Services Task Force 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 than advice from a single specialty group.
Regarding breast cancer screening, the task force recommends:
- A mammogram every 2 years for women ages 50 to 74.
- No routine screening mammograms for women in their 40s, unless they have an increased risk of breast cancer.
- Discussion between a woman and her doctor about whether to screen for breast cancer before age 50. Decisions would be based on a woman's risk of breast cancer and what she prefers after learning about the benefits and harms.
The American Cancer Society and other well respected medical groups vehemently disagree. They say that the task force guidelines will miss too many early cancers. They say that this could cost lives. The cancer society recommends a mammogram every year, starting at age 40, for women at average breast cancer risk. It also recommends a yearly clinical breast exam.
What Changes Can I Make Now?
For women at average risk for breast cancer, I will continue to follow the task force guidelines. However, if a woman wanted to start yearly mammograms 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.
Mammograms detect early cancer. They do not prevent cancer. But there are some things you can do to help lower your breast cancer risk:
- Maintain a healthy weight.
- Don't smoke.
- Either avoid alcohol or drink an average of no more than one alcoholic beverage per day.
- Avoid binge drinking, even if the average amount of alcohol you drink is moderate.
- Eat a diet rich in vegetables, especially the green leafy ones. They are rich in folic acid. Folic acid may offset any increased risk of breast cancer if you drink alcohol.
- Stay physically active. Try to find time every day for dedicated exercise.
What Can I Expect Looking to the Future?
Doctors represented by the American College of Radiology read and interpret mammograms. This group's reaction to the new study was predictable. It says there are major flaws in the research and calls the conclusions misleading. It's likely the American Cancer Society will have a similar reaction.
The researchers and the authors of the editorial published with this article recommend continued study of the benefits vs. harms and costs of mammography. Given the continuing controversy, surely this will happen.