Screening breast US finds occult cancers, but false-positives are problematic

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screening breast ultrasound - 281.79 Kb
Mammographically occult cancer detected at screening breast US, 4-mm infiltrating DCIS arrow) in the right breast.

Nearly three years after the state of Connecticut enacted the first breast density notification legislation in the U.S., an analysis of the performance of screening breast ultrasound revealed the modality helped detect small, mammographically occult cancers, according to a study published online June 21 in Radiology. However, overall positive predictive value of screening ultrasound was low and fewer than 20 percent of eligible women opted for the screening exam.

The Connecticut law requires radiologists to provide women undergoing mammography with breast density information, and a separate law requires insurance companies to pay for screening ultrasound recommended by a physician.

Regina J. Hooley, MD, of Yale University School of Medicine in New Haven, Conn., and colleagues designed a retrospective analysis to determine the utilization and performance of screening breast ultrasound.

The study population included 935 women (mean patient age, 52 years) who underwent a technologist-performed screening breast ultrasound from Oct. 1, 2009, to Sept. 30, 2010. Among this group, 753 women received their breast density notification after a screening mammogram and 182 women were notified after a diagnostic mammogram.

Patient risk factors for breast cancer were low or average risk in 614 women, intermediate risk in 149, high or very strong in 87, and unknown in 85.

Following screening ultrasound, 47 women had 55 lesions classified BI-RADS category 4 and recommended for biopsy. Three cancers were found: a 5-mm ductal carcinoma in situ and 5- and 9-mm invasive ductal carcinomas. Each of these cancers was classified as BI-RADS category 1 on the mammogram and none were retrospectively visible on the mammogram.

The overall cancer yield was 3.2 cancers per 1,000 women screened and overall positive predictive value for all biopsies performed on BI-RADS category 4 lesions was 5.6 percent. According to Hooley et al, the cancer detection rate of the technologist-performed program is similar to that of physician-performed exams.

Radiologists classified 187 women with a BI-RADS category 3 assessment; 131 of these women were followed up for nonsimple cysts.

As part of the study, Hooley and colleagues explored potential methods to reduce the number of ultrasound exams assigned a BI-RADS category 3 final assessment. They re-assigned nonsimple cysts in the setting of multiple cysts and complicated cysts 5 mm or smaller as BI-RADS category 2 and then assessed sensitivity.

A total of 178 of the 187 women with a BI-RADS category 3 result were recommended for six-month follow-up. Among the 145 who returned, four new findings were detected. Seven procedures were performed, and found seven BI-RADS category 4 lesions. However, thus far, no malignancies have been found in any of the lesions initially classified BI-RADS category 3, according to the researchers.

Re-classifying the 79 nonsimple cysts in the setting of multiple cysts as BI-RADS category 2 would have decreased the BI-RADS category 3 recall rate from 20 percent to 11.6 percent. Excluding complicated cysts smaller than 5 mm would have reduced the rate to 9.5 percent, according to Hooley et all.

Hooley and colleagues used current Medicare reimbursement rates for initial screening whole-breast ultrasound, follow-up exams, biopsy and aspiration to derive an estimate for the initial screening breast ultrasound of $180,802 or approximately $60,267 per cancer diagnosed.

The researchers estimated utilization of screening breast ultrasound among eligible women and observed modest uptake. “Approximately 5,697 women were eligible, but only 16.4 percent chose the optional examination.” Furthermore, they wrote, “Only 44.9 percent of patients who underwent screening breast ultrasound at our facility during the study period returned for one-year follow-up screening ultrasound, but 80.6 percent underwent one-year follow-up mammography.”

Hooley et al recommended areas for additional research: validation of their suggested re-classification strategies to reduce the number of BI-RADS category 3 findings and studies to determine the optimal interval for screening ultrasound.