New breast cancer screening guidelines from the American College of Radiology and Society of Breast Imaging advise all women to undergo risk assessment at age 30, followed by screening for those with a greater chance of cancer.
Debra Monticciolo, MD
New breast cancer screening guidelines from the American College of Radiology (ACR) and Society of Breast Imaging (SBI) advise all women to undergo risk assessment at age 30, followed by screening for those with a greater chance of cancer. The guidelines are the first to acknowledge that African American women are at high risk of the disease.
Previous study results have shown that African American women are more likely than non-Hispanic white women to carry a BRCA1/2 mutation, twice as likely to develop aggressive triple-negative disease, and roughly 40% more likely to die from breast cancer, even though incidence rates are similar between the 2 groups.1 BRCA1 mutation is associated with a 50% to 85% increased lifetime risk, and carriers of the BRCA2 mutation have a 45% increased lifetime risk.
Furthermore, African American women are less likely to be diagnosed with stage I disease but twice as likely to die from early breast cancer. Breast cancer mortality in the United States has declined by 43% overall since mammography screening became common in the 1980s, but African American women have not enjoyed the same survival benefit as other patients.
“Since 1990, breast cancer death rates dropped 23% in African American women— approximately half that in whites,” Wendy B. DeMartini, MD, chief of the Breast Imaging Division in the Department of Radiology at Stanford University School of Medicine in California and immediate past president of SBI, said in a statement. “We changed our approach to help save more African American women and others at higher risk from this deadly disease.”
The guideline’s authors concluded that it is especially important for African American women and women of Ashkenazi Jewish descent, both of whom are more likely than the general population to carry BRCA1/2 mutations, to undergo breast cancer risk assessment no later than age 30 so that they can benefit from supplemental screening.2
The ACR and SBI maintain their position that women at average risk of breast cancer should begin screening at age 40. For women aged ≥40 years, screening mammography reduces breast cancer—specific mortality by more than 40%.
“The latest scientific evidence overwhelmingly supports a continued general recommendation of starting annual screening at age 40,” Debra Monticciolo, MD, chair of ACR Breast Imaging Commission, said in a statement. “It also supports augmented and earlier screening for many women. These updates will help save more lives.”
The ACR guidelines list several groups of women who should undergo risk assessment, including those with a first-degree relative who has had cancer, women previously treated with chest or mantle radiation at a young age, women with lobular neoplasia, and women with a BRCA1/2 mutation.The guidelines recommend specific risk-assessment models, noting that all have benefits and drawbacks. The Gail model for assessing the probability that a woman is carrying a deleterious gene mutation takes into account the number of first-degree female relatives with breast cancer and the patient’s history of breast disease, age, ethnicity, and hormonal and reproductive history. This produces estimates of the risk of invasive breast cancer. However, the model requires further validation in Hispanic women, as well as other racial and ethnic groups.
The internet-based statistical model BRCAPRO assesses the probability that a woman is carrying germline BRCA mutations, as well as the risk of developing invasive breast cancer. It is free for research and counseling use but excludes nonhereditary risk factors and genetic mutations other than BRCA. Guideline authors believe that the model may underestimate risk, and some data suggest that BRCAPRO underestimates the likelihood that Hispanic women might carry BRCA mutations.
The Tyrer-Cuzick model, or IBIS (International Breast Cancer Intervention Study), assesses both the probability that a woman is carrying a BRCA mutation and her risk of developing invasive breast cancer. The model includes a detailed first- and second-degree family history and nonhereditary risk factors and allows for multiple genes with variable penetrance. The authors wrote that it is the most comprehensive model.
Different models rely on different data and were developed and validated in different populations, the authors noted. Accuracy will vary widely across populations and in individual women. Even models that have demonstrated good calibration (the ability to correctly estimate expected events with observed events in a population) are just moderately accurate. No current model is well validated for predicting risks associated with breast density.The authors recommend 4 screening modalities for women at elevated risk: digital mammography (DM), digital breast tomosynthesis (DBT), contrast-enhanced breast magnetic resonance imaging (MRI), and ultrasound.
Younger women tend to have denser breast tissue, and the authors wrote that DM is superior to previous film-screen techniques for detecting cancers in dense tissue. Although DBT delivers fewer false positives and detects more cancers than DM alone, there are limited data regarding DBT in women at increased risk. Nonetheless, the authors expect younger, high-risk women to benefit from DBT.
Contrast-enhanced MRI showed a 68% sensitivity for cancer detection in women who carry BRCA1/2 mutations compared with 37% for mammography and 32% for ultrasound. One study showed that, in women carrying the BRCA mutation and those with a ≥20% higher lifetime risk of breast cancer, MRI demonstrated a 90.0% sensitivity compared with 37.5% for both mammography and ultrasound. “MRI has consistently been shown to outperform mammography and ultrasound, even when these latter modalities are used together and in mixed high-risk populations,” the authors wrote.
Multiple trials have demonstrated the value of whole-breast ultrasound for women at increased risk. A systematic review following the passage of Connecticut breast density legislation showed an incremental cancer detection rate of 3.1 to 4.0 per 1000 over the first 4 years. Results from ACRIN 6666, a large prospective multicenter study evaluating women at elevated risk, showed a supplemental cancer detection rate of 4.3 per 1000.
The drawback to ultrasound is a high rate of false positives and poorer positive predictive value (PPV) for biopsy. The false-positive rate in ACRIN 6666 was 8.1% compared with 4.4% for mammography. Mammography was associated with a PPV of 22.6% versus 8.9% for ultrasound.
Whole-breast ultrasound is time- and labor-intensive and operator-dependent, but the hope is that some of these negative aspects will disappear as the technology evolves.