Improving Access to Breast Cancer Screening in the Absence of a Mammogram

Results from ACRIN 6666, a breast ultrasound screening trial, have underscored the importance of using ultrasound for breast cancer screening, especially in regions with poor access to mammography, such as rural areas or in developing countries. Published in the Journal of the National Cancer Institute, the trial found that breast cancer detection rate using ultrasonography (US) is comparable with mammography.

A multicentric, global trial, ACRIN 6666 recruited over 2800 women at 20 sites within the United States, Canada, and Argentina. The protocol included 3 annual screens with US and film-screen or digital mammography, and a biopsy or a 12-month follow-up. A little over 80% of the 111 breast cancers detected were invasive. Importantly, the authors found that 129 US screens (95% confidence interval [CI], 110 to 156) and 127 mammography screens (95% CI, 109 to 152) were necessary to detect 1 cancer. Also, most US-detected cancers were more likely to be invasive (53 of 58), as compared with mammography (41 of 59). Also, invasive cancers detected by US were most often node-negative (34 of 53 compared with 18 of 41) compared with mammography.

Mammography, on the other hand, picked up on cancers that were calcified, most often the non-invasive ductal carcinoma in situ or DCIS. This form of cancer is not usually life-threatening. However, a drawback of US screening, the authors point out, is false positives—only 9% of biopsies following a US confirmed a cancer diagnosis, compared with 29% of biopsies that followed a positive mammogram.

According to Wendie A. Berg, MD, PhD, lead author on the study, “It’s likely the cancers we find on ultrasound will make a bigger difference than those we find in mammography.” In her opinion, if US becomes more common, considering the high rate of false positives, doctors will not conduct a biopsy unless the suspicious region in the image changes over time.

While additional, large-scale studies will be necessary to confirm the usefulness of US as a stand-alone screening technique for breast cancer, Berg believes low-tech ultrasound devices could play an important role in screening women in countries where mammograms are just not available.