Ultrasound a supplementary breast cancer screening tool

March 29, 2013 By Jean Weigert, M.D.

Breast cancer is the second most common cancer in American women and the second leading cause of cancer death in women. Although mammography is currently the best breast cancer screening tool available, it is imperfect, particularly, in cases of dense breast tissue. On a mammogram, dense tissue appears white; cancerous tumors also appear white, making it nearly impossible to “see” the tumor; tumors are often hidden behind dense tissue. As a woman ages, her breasts usually become more fatty and less dense on the mammogram.

The difficulty of detecting cancers in women with dense breasts is of concern. Research indicates that breast density is an independent risk factor for breast cancer. Studies found over a five times greater risk of breast cancer in women with dense breasts. This may be due to both the difficulty in recognizing the abnormality on the mammogram as well as the fact that some types of this dense fibrocystic tissue are more metabolically active and therefore more prone to becoming malignant.

Additional imaging modalities may help find these hidden cancers. Ultrasound has not historically been used for breast cancer screening; however, it has the potential to help detect cancers because it provides better contrast in this dense tissue than does mammography. A national study published in 2008 demonstrated that the addition of ultrasound imaging to screening mammography detected an additional 4.2 cancers per 1,000 high-risk patients than did mammography alone. In addition, a separate study showed that 90 percent of breast cancers detected using ultrasound alone were without spread to other parts of the body including lymph nodes. This result suggests that ultrasound detects early stage cancers, and may have a large potential to reduce breast cancer incidence and deaths.

In October 2009 Connecticut became the first state in the nation to require mammogram reports inform women of their breast density. Connecticut General Statue Sections 38a-530 mandates that every woman in Connecticut who has a mammogram that demonstrates greater than 50 percent breast density must be informed, “If your mammogram demonstrates that you have dense breast tissue, which could hide small abnormalities, you might benefit from supplementary screening tests, which can include a breast ultrasound screening or a breast MRI examination, or both, depending on your individual risk factors… .” Subsequently, New York, Texas, Virginia and California have passed similar legislation.

Since implementing legislation, published research, conducted by me and a Yale-New Haven hospital radiologist, cites that the addition of screening breast ultrasound in women with greater than 50 percent breast density yielded detection of an additional 3.2 and 3.25 breast cancers per 1,000 women screened in this population. Our additional research has demonstrated, for the second consecutive year, an increase in both incidence and prevalence in cancers with the addition of screening breast ultrasound with fewer false positive biopsies. This is important if ultrasound is to be considered a true screening tool.

Although still controversial, it appears that the addition of bilateral breast ultrasound to mammography in women with dense breast tissue significantly improves cancer detection. Future research must be performed to analyze possible long-term benefit of using ultrasound in women with mammographically normal but dense breasts.

Dr. Jean Weigert is a member of The Hospital of Central Connecticut (HOCC) medical staff. For referrals to HOCC physicians, please contact our free Need-A-Physician referral service by phone at 800.321.6244.