Do women need mammograms?
Once a year, thousands of women subject their breasts to the ritual ordeal of poking, prodding, and viselike squeezing known as a mammogram. They willingly endure this process because they know--or at least hope--that if they do get breast cancer, a mammogram will pick it up early enough to treat it and save their lives.
Although much research has found that mammograms do reduce the risk of dying from breast cancer over the long term, these screening tests can have false-positive results, which could lead to unnecessary tests or treatments. Considering the risks and benefits, is it worthwhile to have routine mammograms?
For women over 50, mammograms are worth having, says Barbara Smith, director of the Breast Program at Massachusetts General Hospital and associate professor of surgery at Harvard Medical School.
"The women who die of breast cancer are predominantly women who didn't have mammograms," she says. "If you're waiting until the tumor is big enough to feel by touch, your chance of dying is greater."
A couple of recent studies back up the value of having regular mammograms.
THE EVIDENCE FOR MAMMOGRAMS
A Swedish study published in the journal Radiology in 2011 was the longest ever trial of mammograms for breast cancer detection. It was also the first to track the effects of this screening method alone on breast cancer mortality.
After following more than 133,000 women, ages 40 to 74, over a period of nearly 30 years, the researchers found that women who had a mammogram were 30 percent less likely to die from breast cancer compared to women who didn't have mammograms. For every 414 women screened with a mammogram over a 7-year period, one breast cancer death was prevented.
The authors say most of the deaths prevented were over the long term--after the first 10 years of follow-up. Following women for three decades allowed the researchers to study the effects of mammogram diagnosis on slower-growing breast cancers.
Another positive study, this one from the Netherlands, matched 755 women who had died from breast cancer with more than 3,700 control women. All of the women were age 49 or older when they were diagnosed or screened. The results, which were published in the journal Cancer Epidemiology, Biomarkers and Prevention, suggested that mammograms might lower the odds of dying from breast cancer by about half.
Both of these studies credited mammograms with cutting the risk of dying from breast cancer. Yet other research has raised a few red flags about this test.
A 2010 Norwegian study, which was led by researchers at the Harvard School of Public Health, also found a lifesaving benefit from mammograms--although it wasn't as significant. The researchers looked at data from about 40,000 women who took part in the Norwegian breast cancer screening program.
The study found that mammogram screening only reduced the rate of breast cancer death by about 10 percent in women ages 50 to 69. The reduction was less--8 percent--in women over age 70. Yet a follow-up to the study released this April noted that six to 10 out of every 2,500 women screened were "overdiagnosed," meaning tumors were found and treated that were never likely to become life threatening.
A 2011 analysis of seven mammogram studies found a 15 percent reduction in deaths among women who had the screening test compared to those who didn't, but women who had mammograms were also 30 percent more likely to undergo unnecessary tests or treatments due to false-positive results. Overall, the study found that mammogram screening only extended the life of one out of every 2,000 women, while it led to unnecessary tests and treatments in 10 of those women.
Yet Dr. Smith says false-positive results are a risk with any medical test that's designed to find disease early.
"If you wait until the tumor is huge and obvious, you won't get a false positive, but you'll have waited so long the cancer will have spread," she commented. Because surgeons are moving away from open biopsies in favor of less invasive procedures such as core needle biopsies, even if you need to have further tests, the risks involved are lower, Dr. Smith says.
REVIEW RISK FACTORS
When discussing with your doctor whether and how often to have mammograms, take into account your breast cancer risks, which include:
1. Your age. Most aggressive breast cancers are found in women 55 or older.
2. Your genes. Up to 10 percent of breast cancers are inherited, most commonly from mutations in the BRCA1 and BRCA2 genes.
3. Your family history. Having a mother, sister, or daughter with breast cancer increases your risk.
4. Your cancer history. If you've had cancer in one breast, you're three to four times more likely to develop it again in the same or the other breast.
5. Your breast density. Women with denser breasts are more likely to get breast cancer, and their cancer may be harder to spot on a mammogram.
6. Your use of hormone therapy. Taking combined hormone therapy after menopause increases breast cancer risk.
TO TEST OR NOT TO TEST?
Though they can pick up early breast cancers, mammograms aren't guaranteed to save your life. Screening can miss up to 20 percent of tumors, especially if you have very dense breasts. Or they can detect a cancer that isn't there, potentially sending you for an ultrasound or biopsy when you don't need it. And finally, mammograms expose you to small amounts of radiation (although the risk of getting cancer from a mammogram is negligible).
You, like many women, may be willing to accept these risks in exchange for the chance that the test will pick up breast cancer early, when it's more treatable and before it has a chance to spread. Leading health organizations agree.
Here are their recommendations based on the available evidence:
The National Cancer Institute advises all women age 40 and over to have a mammogram every one to two years.
The American Cancer Society recommends yearly mammograms starting at age 40 and continuing for as long as a woman is in good health.
The U.S. Preventive Services Task Force recommends mammograms every other year for women ages 50 to 74, but says there's not enough evidence to recommend regular mammogram screenings in women ages 75 and older.
Because the frequency and age ranges for testing vary by organization, it can be hard to know which recommendation to follow. Dr. Smith goes by the American Cancer Society guidelines, advising all of her female patients age 40 and older to have annual mammograms.
Should you stop having mammograms after age 75, as the U.S. Preventive Services Task Force recommends?
"If anything, the risk of breast cancer goes up every year a woman is alive," Dr. Smith says. "To say that you stop checking at 75, when the average life expectancy of a woman in this country is in the mid-80s, doesn't make sense to me." As long as you're healthy enough to tolerate a lumpectomy under local anesthesia--should you need it--Dr. Smith recommends that you continue to get annual mammograms in your 70s and beyond.
Although there has been a great deal of debate surrounding mammograms, ultimately the goal of having this screening test is to find tumors early.
"Breast cancer is a very common cancer. The treatments are easier if the tumors are smaller," Dr. Smith says.
Mammography techniques are improving, too. Newer scans in development, such as molecular breast imaging and tomosynthesis (which creates a three-dimensional image of the breast) may soon improve the accuracy of breast cancer diagnosis and reduce the risk of false-positive results. - Harvard Women's Health Watch