Screenings for several forms of cancer, such as of the prostate and ovaries, get low marks in our new Ratings of cancer screening tests, because their risks clearly outweigh the benefits for most people. But the decision whether to get a mammogram to check for breast cancer is especially complex, as illustrated in three recent reports in the British Medical Journal.
The problem is that not all breast cancers are equally aggressive. Some are deadly, some never develop into anything life-threatening, some go away on their own. But mammograms can't always tell them apart. So while the test can save lives, it also leads to additional tests and treatments, many of which are unnecessary. That unnecessary testing and treatment is worrisome, since it poses risks, including exposure to radiation and complications of surgery and hormone therapy. The question is how often does that overtreatment happen.
One of the new reports cites research from an independent panel of experts, which concluded that about 20 percent of women ages 50 to 70 who get diagnosed with breast cancer will end up being overtreated. But a dissenting editorial, written by Michael Baum, M.D., a professor of surgery at the University College London, says that overtreatment is closer to 50 percent. And he also says that the risks of treatment, including radiation exposure to the heart and lungs from radiation therapy, is underestimated.
That difference in overtreatment rates is important, according to the third BMJ report. In that study, researchers found that most women said that they would get screened if the risk of overtreatment was 20 percent, but many would not if it was 50 percent.
And regardless of the exact numbers, women often aren't told about the risks and limitations of the test, only the possible benefits, according to Cliona Kirwan, M.D., a surgical oncologist with the UK's National Institute for Health Research. That's wrong, since a risk that's OK to one person might not be to another. "The level of risk that is acceptable will vary for the individual woman," Kirwan writes, "and the decision on whether to participate in screening is a personal one."
It's unclear how the BMJ research applies to women in the U.S., in part because women in the U.K. tend to get screened every three years starting at age 50, while here screening is usually every year or two, and often starts at age 40. "That more aggressive approach to screening might find more cancers," says John Santa, M.D., director of the Consumer Reports Health Ratings Center. "But it might also lead to even more overtreatment. More modern approaches to screen and treat breast cancer should not follow the old cookbook approach of everybody getting everything."
Our report on cancer screening is meant to provide people with information on the risks and benefits of mammography as well as several other common cancer tests. Our investigation revealed confusion among both doctors and patients about the latest screening guidelines.
Harms from breast cancer screening outweigh benefits if death
caused by treatment is included [BMJ]
Women's views on overdiagnosis in breast cancer screening: a
qualitative study [BMJ]
Breast cancer screening: what does the future hold? [BMJ]