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Supplemental ultrasonography for breast cancer screening may cause more harm than benefit
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Performing ultrasonography as an adjunct to screening mammography increased the risk for false-positive biopsies in women at low, intermediate, and high breast cancer risk, according to research published in JAMA Internal Medicine.
“Whole-breast ultrasonography has been advocated to supplement screening mammography to improve outcomes in women with dense breasts,” Janie M. Lee, MD, MSc, associate professor of radiology at the University of Washington, and colleagues wrote.
However, “accurate information on the effectiveness of screening ultrasonography is needed to provide guidance on whether widespread use of screening breast ultrasonography with screening mammography would be a beneficial strategy,” they added.
Lee and colleagues conducted an observational cohort study using data from two Breast Cancer Surveillance Consortium registries to compare the performance of screening mammography plus same-day screening ultrasonography vs. screening mammography alone in community practice among women across the spectrum of breast cancer risk.
The researchers propensity score matched 6,081 screening mammography plus screening ultrasonography examinations in 3,386 women to 30,062 screening mammograms without screening ultrasonography in 15,176 women at a 1:5 ratio.
Patients with a personal history of breast cancer and self-reported breast symptoms were excluded from the study.
Women with dense breasts (74.3% vs 35.9%), women who were younger than 50 years (49.7% vs. 31.7%) and women with a family history of breast cancer (42.9% vs. 15%) were more likely to receive screening mammography with ultrasonography examinations than screening mammography alone.
Screening ultrasonography examinations were performed in 21.4% of women with high or very high ( 2.5%) Breast Cancer Surveillance Consortium 5-year risk scores, compared with 53.6% of women with a low or average (< 1.67%) risk.
The cancer detection rate (5.4 vs. 5.5 per 1,000 screens; adjusted RR = 1.14; 95% CI, 0.76-1.68) and interval cancer rates (1.5 vs. 1.9 per 1,000 screens; RR = 0.67; 95% CI, 0.33-1.37) were similar among patients receiving mammography plus ultrasonography and mammography alone.
There were significantly higher rates of false-positive biopsy (52 vs. 22.2 per 1,000 screens; RR = 2.23; 95% CI, 1.93-2.58) and short-interval follow-up (3.9% vs. 1.1%; RR = 3.1; 95% CI, 2.6-3.7) in the mammography plus ultrasonography group. Additionally, the predictive value of biopsy recommendation was significantly lower in the mammography plus ultrasonography group (9.5% vs. 21.4%; RR = 0.5; 95% CI, 0.35-0.71).
“These results suggest that the benefits of supplemental ultrasonography screening may not outweigh associated harms,” Lee and colleagues concluded.
“To apply supplemental ultrasonography screening with greater effectiveness, we suggest that additional efforts are needed to more accurately identify women who will benefit from supplemental screening,” they added. “We also suggest that development is required of the capacity to deliver high-quality supplemental screening, as well as new interventions to reduce the frequency of screening-related harms.” – by Alaina Tedesco
Disclosures: Lee reports receiving grants from the American Cancer Society and National Cancer Institute, as well as grants, personal fees and nonfinancial support from GE Healthcare. Please see the study for all other authors’ relevant financial disclosures.
Perspective
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Deborah J. Rhodes, MD
Real-world analysis of supplemental screening with whole breast ultrasound (WBUS) is particularly important because this modality is known to be highly operator-dependent. While randomized controlled studies in which radiologist training and ultrasound protocols are well standardized have demonstrated a modest increase in cancer detection yield for WBUS, this study by Lee et al of WBUS in U.S. community practice found that cancer detection rates were almost identical in the group who received WBUS compared to a matched group who received only screening mammography, while the false-positive biopsy rate was more than double in the WBUS group.
The authors conclude that to make supplemental WBUS more effective, efforts should be directed at identifying a subgroup of women most likely to benefit and improving the quality standards of the test. This conclusion seems erroneous given that a large U.S. trial (Berg et al, JAMA 2012) found that even when quality standards are rigorously optimized, the addition of WBUS to mammography still fails to detect a sizeable reservoir of invasive cancer in intermediate-risk women with dense breasts — a reservoir as large as 11 additional invasive cancers per 1,000 women screened, or more than double the total number found by the combination of mammography and WBUS.
This is a limitation, not of the population or imaging protocol studied, but of the WBUS test itself. The majority of women who develop breast cancer do not have a family history of breast cancer, so limiting supplemental screening with WBUS to a subgroup at higher risk is not likely to sway the WBUS risk-benefit equation convincingly. Instead, efforts should be directed at supplemental screening with a functional modality that exploits differences in tumor cell function to detect cancers occult on anatomic modalities (which includes mammography, digital breast tomosynthesis and WBUS).
Trials of MRI and molecular breast imaging (MBI), both functional modalities, have demonstrated substantial increases in invasive cancer detection compared to mammography alone. Concerns about MRI cost and recall rate have prompted the ACRIN EA1141 trial which will soon report results comparing abbreviated MRI (which is lower in cost than standard MRI) to digital breast tomosynthesis in women with dense breasts.
Concerns about multicenter performance and radiation dose of MBI will be addressed in the Density MATTERS trial for which recently presented interim results look promising. Rather than doubling up on two anatomic techniques each with its own set of limitations, efforts should be directed at establishing a cost-effective functional screening modality that eliminates the reservoir of occult cancers and reduces unnecessary biopsies, thereby overcoming the limitations of both mammography and WBUS.
Reference:
Berg WA, et al. JAMA. 2012;doi:10.1001/jama.2012.388.
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