Digital Mammography Finds More Invasive Breast Cancers

Digital mammography is better for detecting life-threatening breast cancers than is screen film mammography, without significantly increasing detection of clinically insignificant disease, according to a study published in the online issue of Radiology.

Researchers from the Netherlands compared digital mammography (DM) with screen film mammography (SFM) in almost two million mammograms performed between 2003 and 2007. They found that recall was indicated in 18,896 women, and 6,410 women were diagnosed with breast cancer. The DM had a higher initial sensitivity for detecting the breast cancer, with a detection rate of 6.8 per thousand, compared with 5.6 per thousand with SFM.

“More DCIS [ductal carcinoma in situ] and invasive cancers are detected with the use of DM in breast cancer screening compared to SFM,” said Adriana M.J. Bluekens, MD, from the National Expert and Training Centre for Breast Cancer Screening in Nijmegen and St. Elisabeth Hospital in Tilburg. “In the mix of low- to high-grade DCIS lesions, there is no shift to the detection of low-grade lesions in digital screenings. Instead of this, we noticed a larger amount of high-grade lesions, which are regarded as precursors of high-grade invasive tumors.”

With digital mammography, the detection of high-grade DCIS was 58.5 percent, compared with 50.5 percent with screen film mammography.

There has been concern about overdiagnosis of clinically unimportant breast cancers when using screening procedures such as DM. In this study, the initial recall rate was higher with DM at 4.4 percent compared with 2.6 percent with SFM. However, the researchers found that there was no disproportionate increase in low-grade DCIS lesions.

Bluekens pointed out, though, that the follow-up period is not long enough yet to be able to determine mortality effect of DM separate from SFM. “However, surrogate parameters, such as stage distribution and tumor characteristics of DM-detected cancers, do indicate the continuation of mortality decrease with the transformation of SFM to DM in screening programs.”