David Brill
Adding ultrasound to standard mammography for breast screening will identify more cancers but also lead to more false alarms, according to research published in the Journal of the American Medical Association.
The study, conducted by the American College of Radiology Imaging Network, found that a combined protocol would yield an extra 4.2 cancers for every 1,000 women screened compared to mammography alone (95 percent confidence interval 1.1 – 7.2; P=0.003). Combining ultrasound with mammography, however, increased the false positive rate from 4.4 percent to 10.4 percent. [JAMA 2008 May 14;299(18):2151-63]
Dr. James Khoo, head of the department of oncologic imaging at the National Cancer Centre Singapore, said that this increase was a concern.
“From mammography alone you would be doing a certain number of biopsies, but if you add ultrasound the number of biopsies would increase significantly and the vast majority would be benign results,” he said.
Khoo added that being recalled for extra tests is “a very fearful experience” for most women, and that feelings of anxiety can persist for a long time even once a lesion is identified as benign.
The study analysis comprised 2,637 women at high risk for breast cancer, who were followed up for 12 months. Of these 275 were recommended for an unnecessary biopsy after combined screening, compared to 116 who were screened with mammography alone.
Although combined screening increased the diagnostic yield in the study it did not detect all cancers: eight women out of 40 who were ultimately diagnosed with cancer had lesions that were not detected on either modality.
Previous research suggested that women at high risk for breast cancer should be monitored using mammography and magnetic resonance imaging (MRI). [J Clin Oncol 2005 Nov 20;23(33):8469-76]
Although unlikely to replace MRI in these patients, ultrasound could be used in addition or as an alternative when MRI is contraindicated, said Khoo.
Ultrasound is well tolerated, relatively inexpensive and widely available, and has the potential to detect small node-negative cancers which can be missed by mammography. However the technology is hindered by high inter-observer variability and a low sensitivity for detecting microcalcifications, such as those seen in ductal carcinoma in situ.
In an accompanying comment in the journal, Christiane Kuhl from the University of Bonn in Germany wrote that: “Individualized screening schemes tailored to the individual risk and to the personal preferences of a woman may be the way to consider how to screen for breast cancer.
“Whether in the long run, ultrasound or breast MRI will be more appropriate for this purpose remains to be seen,” she concluded
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