Digital breast tomosynthesis (DBT), a technique that produces 3-D images of the breast, could reduce the number of women who undergo biopsies to look for cancer after they have an abnormal mammogram, according to a study published in the journal Radiology.
“DBT allows for improved reader accuracy and confidence in determining if a mammographic abnormality is concerning for cancer or not, leading to a reduction in the number of biopsies performed,” said lead researcher Nisha Sharma, MBChB, director of breast screening at Seacroft Hospital in Leeds, England.
Women in England are called for routine screening mammography every three years between ages 50 and 70. Typically, when an abnormality is seen on a mammogram, the woman is called back for a triple assessment that includes a clinical breast exam and additional mammography and ultrasound imaging followed by a biopsy if needed. A biopsy involves removal of a small sample of tissue to examine in the lab to determine whether it’s malignant, or cancerous.
Fortunately, in a majority of cases, the abnormality turns out to be benign. More sensitive methods could help rule out cancer without the need for so many biopsies, which come with added cost, inconvenience, discomfort and a small risk of complications.
Sharma’s team evaluated the effect of adding DBT to the usual triple assessment for women who were called back after initial breast screening using conventional full-field digital mammography (FFDM).
FFDM captures two digitized images of the breast, from top to bottom and from side to side. DBS uses low-dose x-rays to take multiple images of the breast from different angles, which are used to construct a 3-D image.
“The thin slice images of the breast taken with DBT reduce the effect of tissue overlap, which often leads to cancers being missed or to women who don’t have breast cancer being recalled for diagnostic imaging,” Sharma said in a press release from the Radiological Society of North America.
This study included nearly 40,000 women who received care at a single National Health Service facility. They underwent screening with FFDM or magnetic resonance imaging (MRI) between November 2015 and July 2016.
Of these, 1,470 women, or 4.8 percent, were called back for further evaluation of suspicious findings. Within this group, 827 women who agreed to participate in the study received DBT in addition to the usual triple assessment.
Based on the triple assessment without DBT, 571 women underwent breast biopsies, leading to the confirmation of 142 breast cancers. That is, three fourths of the biopsies showed that the suspicious abnormalities were not cancerous—a benign biopsy rate of 75 percent.
Sharma’s team then asked whether also considering the DBT results would have influenced biopsy recommendations. In order to reduce bias, the radiologists who read the DBT images did not know the initial FFDM screening or biopsy results.
The researchers calculated that adding DBT would reduce the number of biopsies to 298 while still detecting all cases of cancer. The proportion of women undergoing biopsies would have decreased from 69 percent to 36 percent, and the benign biopsy rate would have fallen to 52 percent. Compared with FFDM, DBT had a significantly higher specificity, or ability to rule cancer when it is not present (38.2 versus 77.5 percent, respectively).
“Our study validates that DBT can help in the diagnostic workup of mammographic abnormalities and reduce harm to women through fewer false positive biopsies without any reduction in the cancer detection rate,” Sharma concluded.
Click here to read the study abstract.