Traditional mammography continues to be the gold standard for breast cancer screening technologies. However, use of 3-D breast tomosynthesis is growing rapidly.
The importance of early detection of breast cancer has been underscored in recent years as the breast health community learns more about breast density and risk models, turning toward personalized medicine. As this knowledge base expands, healthcare professionals are exploring the benefits of different imaging technologies to improve detection and save lives.
Mammography continues to be the gold standard for breast cancer screening technologies, but recent discussions have debated how often women should be screened and/or the need for supplemental imaging.
In 2016, the U.S. Preventive Services Task Force (USPSTF) released controversial new recommendations for mammography screening practices. In addition to suggesting biennial screening is sufficient for women in their 40s — going against conventional wisdom — the task force posited the balance of benefits versus harms for mammography screening in women over age 75 was inconclusive.
A large study presented at the 2018 Radiological Society of North America (RSNA) annual meeting in November suggests that women over 75 do benefit from continuing screening, depending on their circumstances, due to a high incidence of breast cancer. The study, from Elizabeth Wende Breast Care in Rochester, N.Y., looked at more than 750,000 mammography exams performed between 2007 and 2017. A subset analysis of nearly 77,000 patients age 75 and older found a total of 645 malignancies in 616 patients for a cancer rate of 8.4 detections per 1,000 exams in this age group. The cancer rate for the entire patient cohort was only 5 detections per 1,000.
“We think it’s very important for women in their 70s to understand there is still benefit to annual screening mammography,” said Stamatia Destounis, M.D. “Right now in the United States, a 75-year-old woman may live another 10 years. If you’re in good enough health to be able to take care of your family and go to work and everything else, you can come in and have a screening mammogram that takes a few minutes.”
Destounis also noted that cancers found in the older age group were predominantly invasive (7 percent lymph node metastasis rate), evaluated as grade 2-3 lesions. You can watch a video, “Women Benefit From Mammography Screening Beyond Age 75,” with Destounis at https://bit.ly/2R7swTR.
One of the main reasons breast cancer screening has shifted to a more personalized approach in recent years is the further understanding of the role of fibroglandular breast density in masking cancer. On a conventional 2-D mammogram, both dense tissue and cancerous tissue appear white, making the cancer mammographically occult.
Quantitative assessment of breast density can improve cancer detection rates, as seen in an RSNA 2018 study. The case-control study of 1,204 U.K. women ages 50-74 assessed breast density using a visual analog scale of 0 to 100, BI-RADS 5th Edition density categories and fibroglandular volume (FGV) calculated by Volpara software. Study results showed that FGV predicted both screen-detected and interval cancers. The other methods predicted interval cancers but not screen-detected cancers.
Contrast-enhanced Spectral Mammography
Contrast-enhanced spectral mammography (CESM), or contrast-enhanced digital mammography (CEDM), has provided an alternative to traditional mammography since 2011 when the first CESM system was approved for the U.S. market. Contrast dye injected into the breast is often taken up by lesions, making them easier to spot.
A study presented at RSNA 2018 demonstrated that CEDM can help safely reduce the number of benign breast biopsies, which can cause physical pain and stress for patients. Under the current (5th) edition of the American College of Radiology’s Breast Imaging-Reporting and Data System (BI-RADS), if a detected lesion is classified as BI-RADS 4 or 5, a biopsy is recommended. An estimated 20-25 percent of BI-RADS 4 suspicious lesions do not turn out to be malignancies, however, making biopsies universal is not ideal at this level.
The study looked at 57 women (ages 34-74) with 60 BI-RADS 4A or 4B soft tissue lesions scheduled for ultrasound, stereotactic or tomosynthesis directed biopsy, and CEDM was performed immediately prior to biopsy. Four MQSA-qualified radiologists provided 3 BI-RADS scores for each lesion: mammography/digital breast tomosynthesis (DBT) only, with ultrasound added and with CEDM added.
Prior to CEDM, 72 percent of the ratings were classified as BI-RADS 4; after CEDM, 60 out of 240 total ratings were reclassified as less than BI-RADS 3.
For women with dense fibroglandular breast tissue, masking increases the likelihood that cancers could be missed on a mammogram. Ultrasound has offered an alternative, found to detect some 30 percent of cancers missed on mammography.
While breast ultrasound has proven effective in the short-term, little is known about its long-term performance. Destounis presented a second study at RSNA 2018 that tracked the performance of screening breast ultrasound over a five-year period at her clinic in New York.
The retrospective study assessed data from 23,878 screening ultrasound exams performed between 2013 and 2017 in patients with heterogeneously dense or extremely dense breasts. Destounis and her team were interested in the cancer detection rate (CDR), positive predictive value (PPV) and biopsy rate for lesions detected with ultrasound only.
Cancer detection rate did increase over the first three years of the study, from 1.4 cancers per 1,000 to 3.6 per 1,000, then decreased in 2016 and 2017 to 2.4/1,000 and 2.2/1,000, respectively. It should be noted that use of digital breast tomosynthesis (DBT) increased dramatically in the study population over the five-year period, from 18.7 percent in 2013 to 99.3 percent in 2017. The research team suspects that the improved detection provided by DBT may have led to the decline in ultrasound-only detected lesions in subsequent years.
The biopsy rate did decrease steadily over the five-year period, from 2.9 percent to 1 percent in 2017. PPV for biopsy fluctuated in the study period, jumping 15 percent in the first year, declining slightly over the following two years, then increasing again in the final year, ultimately rising from 5 percent to 22.3 percent. This suggests that biopsies were employed more efficiently over the course of the five-year period.