Ultrasound Spots Cancers Overlooked by Mammography

CHICAGO--Although mammography is the best screening tool for breastcancer, it misses carcinoma in 15% or more of women with dense breasts.Supplemental, bilateral, high-resolution ultrasound can find these malignancies,Thomas M. Kolb, MD, a New York City radiologist who specializes in breastcancer detection, reported at the Radiological Society of North Americameeting.

In a study by Dr. Kolb and his colleagues Drs. Jacob Lichy and JeffreyNewhouse, ultrasound examination of women with dense breasts who had normalmammograms and no abnormalities on physical examination increased the detectionof breast cancer by nearly 16% and raised by 30% the number of tumors detectedby imaging only.

Ten of 250 Masses Malignant

Follow-up ultrasound studies detected 250 solid masses that had notbeen observed on mammography or palpated during physical examination of2,600 women with dense breast tissue. Ten of these masses proved to bemalignant at biopsy.

Ultrasound also spotted breast tumors that were small in size and atan early stage. The average size of the malignancies found with ultrasoundwas 11.3 mm, which was nearly identical to the 11.2 mm average size forcancers observed on mammography and about half the size of tumors thatwere found by palpation.

Eighty-seven percent of the malignancies seen on ultrasound were stage0 or stage 1, compared with 92% of the tumors detected with mammography.But only 40% of palpable tumors were low stage.

Ultrasound is especially helpful in the evaluation of women with densebreasts. "The sensitivity of the mammogram is reduced in these womenbecause breast cancer that appears white on the mammo-gram can be hiddenin dense glandular tissue, which is also white," Dr. Kolb said. (SeeFigure 1.)

Fortuitously, he added, the appearance of a cancer on ultrasound isjust the opposite; it is dark, which stands out in a white background,"allowing us to detect cancers in dense breasts that would have beenotherwise missed." (See Figure 2.)

In his study, assuming $150 for ultrasound, $300 for an ultrasound-guidedbiopsy, and $1,500 for surgical biopsy, each of the 10 cancers detectedwith ultrasound by Dr. Kolb cost $36,000 over and above the cost of screeningmammog-raphy and physical examination. "It is important to understandthat an ultrasound examination does not replace a mammogram but rathermay add additional information," he said.

Dr. Kolb hesitated to recommend routine ultrasound screening: "Beforewidespread use of the technique is instituted, analysis of mortality reductionand a more thorough cost analysis are necessary."