Washington, May 14 : Combining ultrasound screening with routine mammography may help in more effective diagnosis of breast cancers, but can also increase the rate of false positive findings, says a new study.
The clinical trials over 2,809 women in 21 clinical sites in the United States, Canada and Argentina were conducted by the American College of Radiology Imaging Network (ACRIN) and analyzed by Brown University statisticians.
The participants were women aged 25 years or older and were at an increased risk of breast cancer, women with dense breasts, women with a family history of breast cancer, and women who'd already had a breast biopsy.
"The trial uncovered a significant trade-off with ultrasound screening," said Jeffrey Blume, an associate professor in the Department of Community Health and the deputy director of the ACRIN Biostatistics and Data Management Center at Brown.
"While supplemental ultrasound screening uncovers more breast cancers, it also substantially increases the risk of a false positive cancer finding and unnecessary biopsy.
"The medical community may well decide that the screening benefit is offset by the increase in risk to women from a false positive finding," said Blume.
"However this study also shows that supplemental ultrasound may be beneficial in women at high risk of breast cancer who could not, or would not, otherwise undergo a magnetic resonance imaging scan. Women should consult their doctor for more information," he added.
Ultrasound screening uses high frequency sound waves to depict and detect tumours, while mammography uses low-dose X-ray.
During the first year of screening, mammography alone revealed breast cancers at a rate of 8 for every 1,000 women screened and resulted in 25 women for every 1,000 screened having an unnecessary biopsy due to a false positive exam.
The combination of mammography and ultra-sound revealed breast cancers at a rate of 12 for every 1,000 women screened and resulted in 93 women for every 1,000 screened having an unnecessary biopsy due to a false positive exam.
The study showed a four-fold increase in false positive findings with 68 additional women for every 1,000 screened.
"This false positive rate is significant, said Blume.
"And the combination of screening exams, both mammography and ultrasound, still missed one out of every five cancers. So the trial shows that ultrasound is not a silver bullet for breast cancer screening," he added.
The findings appear in May 14 issue of the Journal of the American Medical Association.