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, US researchers said.
"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.
Finds invasive cancer
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 centres 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 standardised 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 mammograms alone or a 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.
Also increase false positives
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 (R7 600 to R11 400) 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. – (Julie Steenhuysen/Reuters Health)
Alternative to breast biopsy