CHICAGO (Reuters) - Using ultrasound in addition to mammography helped doctors spot significantly more breast cancers in high-risk women compared with mammograms alone, but it also resulted in four times as many false alarms, U.S. researchers said on Tuesday.
"Mammograms saw only half of the breast cancers that were present. If we added ultrasound to mammography, we saw 78 percent of the cancers," said Dr. Wendie Berg of American Radiology Services at Johns Hopkins Green Spring in Lutherville, Maryland, who led the study.
Berg said most of the cancers they found with ultrasound were small invasive cancers that had not yet spread to the lymph nodes. "These are types of cancers that we most need to be finding," said Berg, whose study appears in the Journal of the American Medical Association.
"Ultrasound does very well at finding invasive cancer," she said in a telephone interview.
The study was designed to see whether ultrasound might improve the chances of finding breast cancer in high-risk women with dense breast tissue, which makes cancer harder to see on a standard mammogram, a type of X-ray.
Smaller studies at individual centers had reported success with this approach, but Berg wanted to see if those findings could be repeated in a large study.
Ultrasounds can be tricky.
"It's a real-time examination that depends on the person doing the scanning to perceive an abnormality while they are doing it. No amount of looking at the picture later will compensate for that," Berg said.
For her study, Berg and colleagues standardized the scanning technique and interpretation criteria for the ultrasound exam. They studied 2,809 women from April 2004 to February 2006 at 21 sites, who underwent mammogram alone or mammogram plus an ultrasound.
Women in the study were 25 or older and had dense breasts, meaning at least half of the breast was made up of tissue other than fat.
Within the first year of screening, 40 women were diagnosed with breast cancer. Mammography alone found 12 cancers; mammography plus an ultrasound found 20 cancers, and the screening tests missed seven cancers caught on later screening and one cancer detected when a lump was felt.
Adding ultrasound increased the rate of false positives fourfold. About one in 40 women who got a mammogram alone had an unnecessary biopsy, Berg said. In the group that got both a mammogram and an ultrasound, that rose to 1 in 10 women.
"That causes a lot of unnecessary stress and of course adds costs to the medical system," Berg said.
She and colleagues plan to do a cost-benefit analysis to determine whether it makes sense to add ultrasound as a routine test for high-risk women. The results are from the first year of a three-year study. In the third year, some of the women also got an advanced test known as a breast MRI.
Some studies have shown a breast MRI can detect breast cancers very early in high-risk women, but they cost $1,000 to $1,500 per test and are currently only recommended for women at extremely high risk of breast cancer. Breast MRIs also have a high rate of false positives.
"Whether in the long run ultrasound or breast MRI will be more appropriate for this purpose remains to be seen," Dr. Christiane Kuhl of the University of Bonn, Germany, wrote in a commentary.
The study reviewed here found that women who are at high risk for breast cancer benefit more from screening with a mammogram AND breast ultrasound than from a mammogram alone.
In high-risk women who got only a mammogram, only half of the breast cancers that were present were found. When both a mammogram and breast ultrasound were done, about 80% of the breast cancers were found. Ultrasound was very good at finding small breast cancers that hadn't spread to the lymph nodes yet. It's always good to find breast cancer early, when it's most treatable.
Finding more breast cancers earlier by adding another screening method, such as ultrasound, is important. But adding another screening test also increases the risk of a "false positive." False positives happen when a screening test identifies an area that looks like cancer, but turns out to be normal.
Research has shown that when more than one screening test is used, there's a greater risk of false positives. In the study reviewed here, women who had both mammogram and ultrasound screening were 4 times more likely to have a false positive than women who had only a mammogram. Besides the fear of being diagnosed with breast cancer, a false positive also means more tests (including biopsies) and follow-up doctor visits. The process can be very stressful and upsetting.
For women who have an average risk of breast cancer, getting a mammogram every year starting at age 40 is a very good way to screen for breast cancer. Women at high risk:
may need different screening plans.
Adding ultrasound is one way to increase the chances of finding a breast cancer early in high-risk women, but it also increases the risk of a false positive. Other studies have shown that a breast MRI scan may be better than mammograms for finding very early breast cancer in high-risk women. Adding MRI also increases the rate of false positives, but this higher rate is considered acceptable by women and their doctors because of the benefits of MRI. The American Cancer Society recommends using MRI screening instead of mammography in certain groups of women at high risk for breast cancer.
If you have a higher-than-average risk of breast cancer, you might want to ask your doctor about:
No matter what your risk of breast cancer is, you and your doctor can work together to create a screening plan that's best for you.
For more information on mammograms, ultrasounds, MRIs, and other tests to find breast cancer, visit the breastcancer.org Screening and Testing section.
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