Ultrasound picks up tumours in dense breasts
CHICAGO - Women should not only get screened for breast cancer with mammography, but they should have ultrasound studies done, some researchers contend.
Ultrasound studies are good at picking up many of the cancers missed by mammograms, especially those which occur in women who have dense breasts.
A study was done in which 18,005 women underwent three types of screening for breast cancer: mammography, ultrasound and physical exam.
A total of 7,202 (40%) had dense breasts. Of those who had cancer from that group, many had early cancer that was missed by mammography alone.
Results of the study were presented at the annual meeting of the Radiological Society of North America by Dr. Thomas Kolb, a radiologist from the Columbia-Presbyterian Medical Centre in New York City.
"No study has quantified the sensitivities for all three screening modalities in a single patient population," he said.
In the study population, 161 were found to have breast cancer, 83% of whom were identified through mammography, and 63% identified through use of ultrasound. Physical exam was able to pick up on only 30% of cases.
Of the women who had dense breasts, 80 cancers were identified in 75 women. Mammography alone helped find 56 (76%) of those cancers, but when combined with ultrasound, 75 (94%) of the cancers were found. The remaining five cancers were found through physical exam, Dr. Kolb said.
How well cancers could be detected with use of mammography was related to breast density. The more dense the breast, the less sensitive the test.
"Breast density was the most significant factor with mammography," Dr. Kolb said. "As density increases, sensitivity decreases."
This is reversed with ultrasound. The test became more sensitive as breast density increased. Women who had breasts that were of a grade I density (more fatty breasts which are the least dense type), mammography detected 97.5% of cancers. With grade IV density (more glandular, dense breasts), the sensitivity dropped to 55%. For breast density of grade I, ultrasound had a sensitivity of 53%, but jumped to 75.1% for breasts that were grade IV.
Ultrasound, used as a screening tool alongside mammography can bring the number of cancers detected up, especially in women who have dense breasts, he said.
In a second presentation at the conference, Dr. Beverly Hashimoto, deputy chief of radiology at the Virginia Mason Medical Centre in Seattle described the merits of using high frequency ultrasound.
While most calcifications can be detected by mammogram, ultrasound is helpful when it comes to figuring out whether the calcifications are cancerous and should be biopsied, she said.
"With high frequency ultrasound, we can find smaller and smaller tumours."
She presented findings from a study of 220 women who had abnormal mammograms. Of that group, 86 were found to have abnormal clusters of calcifications which didn't show any masses on mammograms.
A total of 24 of those women were identified, histologically, as having breast cancer, Dr. Hashimoto said.
Of those 24 cancers, ultrasound was successfully used to identify 20 of them as being cancerous. Out of those 20, 12 were found to have masses which showed up on ultrasound.
While high frequency ultrasound machines are more expensive than the devices most hospitals use, they can catch some of the smaller tumours, and unusual calcifications which may be missed by mammogram. Centres which do breast cancer screening "should have high quality equipment," she said.
The device used in the study had a 8-12 mHZ transducer.
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