Study: How do ultrasound and mammography compare in breast cancer screening?

IN DEPTH REVIEW OF RESEARCH

Study background:

Previous work has shown that mammograms reduce the number of breast cancer deaths. In women from age 40-49, researchers have seen a 15% reduction in breast cancer deaths; a 22% reduction has been seen in women from age 50 -74. It is believed that older women benefit more from mammography because their breasts are not as dense as those of younger women. In addition to ultrasound’s portability and cost benefits, the quality of ultrasound images are not as limited by breast density as are mammography images.

In January 2016, Wendie Berg and colleagues at the Magee-Womens Hospital of University of Pittsburgh Medical Center and other institutions published a study in the Journal of the National Cancer Institute that compared all aspects of cancer detection from ultrasound and mammography.

What researchers of this study wanted to know:

Is ultrasound a viable alternative to mammography?

Population(s) looked at in the study:

This study included 2,662 women who did not have breast cancer, but did have dense breasts. These women also had to have one other risk factor for breast cancer (for example, a BRCA mutation, an atypical breast biopsy, or high risk scores through the Gail test for Breast Cancer Risk Assessment).

Study findings: 

1. One hundred and eleven breast cancers were found in  a three- year period from a total of 7473 breast cancer screens in patients at increased risk for breast cancer. Of these 111 breast cancers, 58 were found through ultrasound and 59 were found through mammography.
2. It took 129 ultrasound screens to detect 1 cancer.
3. It took 127 mammogram screens to detect 1 cancer.
4. 89 of the breast cancers were invasive. Of the 89 invasive cancers, 53 were found by ultrasound and 41 were found by mammography.
   • Fifty-three of the 58 cancers found by ultrasound were invasive; the other five were ductal carcinoma in situ (DCIS). Forty-one of the 59 cancers found by mammogram were invasive; the other 18 were DCIS. These results indicate that ultrasound screening may be better able to identify invasive cancers.
5. There were more false positives found in patients who got ultrasounds compared to patients who got mammograms. The recall rate for ultrasounds was about 11% while the recall rate for mammograms was about 9%.
   • The biopsy rate for the women who got called back based on their ultrasound results was about 6% while it was 2% for women who got called back based on their mammogram results.

Limitations:

In order to participate in this study, women had to have dense breasts and at least one other risk factor for breast cancer, meaning that they were all at greater risk for breast cancer than women in the general population. Therefore, the results of this study may be more applicable to young breast cancer survivors. Had study participants been at average risk for breast cancer, the results may have been different. For now, the results apply only to women at high risk of breast cancer. 

Conclusions:

This study suggests that ultrasound may be a viable alternative to mammography for women in countries that do not have access to mammography. Ultrasound should not be a replacement, however, for women who can access mammography.  The researchers saw that more invasive cancers were detected by ultrasound as compared to mammography; however, they write, “a larger study is needed to statistically support greater sensitivity of ultrasound to invasive cancers.”

Posted 2/16/16