Digital Mammography Plus Tomosynthesis Improves Breast Cancer Screening

August 6, 2013

A new study shows that the combination of digital mammography plus tomosynthesis results in fewer false positive results compared with digital mammography alone. Women under the age of 50 and those with dense breasts had the greatest benefit from the combined screening approach.

A new study shows that the combination of digital mammography plus tomosynthesis results in fewer false positive results compared with digital mammography alone. Women under the age of 50 and those with dense breasts had the greatest benefit from the combined screening approach. The study is published online in the journal Radiology.

At left, a left breast craniocaudal focal compression mammogram showing infiltrating lobular cancer. At right, a craniocaudal tomosynthesis single frame of the same breast showing the cancer in more detail, including the shape and anatomy at the margins.

Brian M. Haas, MD, of the department of diagnostic radiology at the Yale University School of Medicine in New Haven, Connecticut, and colleagues analyzed a total of 13,158 patients, of which 6,100 had both tomosynthesis and digital mammography. The study collected data retrospectively from four sites, and the patients were not randomized.

The rate of recall decreased by 29.7% for those screened with the combination compared with mammography alone (P < .01). The recall rate was 12% for women screened with mammography alone compared with 8.4% for those who were screened using the combined method (P < .01). The recall rate is the rate at which a patient is called back for further biopsy or imaging.

“Tomosynthesis promises to reduce patient anxiety by reducing the number of women who are recalled from screening mammography,” stated the authors. More accurate testing can also help to reduce the cost of additional testing.

The greatest reduction in recall rates was among those with dense breast tissue and women younger than 50 years of age. Recall rates in patients younger than age 50 were 25% for mammography alone compared with 11% for the combination technique.

According to the authors, the combination technique could increase screening compliance in these two sensitive patient populations.

Digital mammography is currently the standard screening technique for breast cancer screening in the United States. According to the National Cancer Institute, screening can reduce death from breast cancer for women between the ages of 40 and 74, based on clinical trial data. Screening is recommended every 1 to 2 years, depending on risk criteria. Like standard mammography, digital mammography produces an image using x-rays. However, this screening method can be problematic, resulting in false positive results for certain women with dense breast tissue. False negative results can also be an issue.

The downside to tomosynthesis is the increase in radiation exposure, which is almost twice as much as that of digital mammography. However, in May, the US Food and Drug Administration (FDA) approved a device that can produce a two-dimensional mammography image using the three-dimensional tomosynthesis data, reducing radiation exposure.

Digital tomosynthesis is approved by the FDA but is still a relatively new technology that is not part of regular screening practice. This technique takes multiple x-ray images of the breast tissue from different angles, allowing for a three-dimensional reconstructed image that can be viewed as individual layers. Tomosynthesis has shown to decrease the rate of false positive results when combined with mammography in several studies over the past few years.

Rates of cancer detection were similar in both screening groups, but the study was not sufficiently powered to show small differences in detection rates. In the current study, in those who were screened using both methods, the cancer detection rate was 5.7 per 1,000 patients, compared with 5.2 per 1,000 patients in those who received mammography alone.

“All age groups and breast densities had reduced risk for recall in the tomosynthesis group,” said Dr. Haas in a statement. “Women with dense breasts and those younger than age 50 particularly benefited from tomosynthesis.”

The lower recall rates were consistent for all women in the study and were statistically significant for all women except those aged 70 or older and those with mostly fatty breast tissue.

The study showed a 38% reduction in risk of recall (P < .0001) when tomosynthesis was combined with mammography compared with mammography alone, after the authors controlled for age, breast density, and other breast cancer risk factors.

The research group is currently in the process of comparing the cancers found on tomosynthesis with those found on mammography. They are also tracking the study group for interval cancers-those that develop in the interval between screenings-to make sure that the reduced recall rate associated with tomosynthesis is not resulting in missed cancers.

A larger trial to better understand the differences in the cancer detection rate and the recall rates is warranted, according to the study authors.