Digital boosts breast cancer detection, recall rates in Europe

Full-field digital mammography yields higher cancer detection and recall rates than conventional mammography, based on large European studies involving thousands of women. Study findings were presented at the RSNA meeting on Tuesday.

Although FFDM recall rates are higher than screen-film, they are still far lower (under 5%) than typical recall rates in the U.S. But it is too soon to tell whether mortality rates will benefit from the higher number of cancers detected, researchers say, and whether digital mammography is efficacious in the screening setting.

"There is no doubt that digital is at least as good as screen-film. We see more, recall more, and detect more cancers, particularly calcifications. That does not necessarily mean you are saving more lives," said Dr. Stefano Ciatto of the Centro per lo Studio e la Prevenzione Oncologica in Florence.

Ciatto presented the findings of a trial involving women aged 50 to 69 participating in a mammography screening program in Florence from 2004 to 2005. The program screens 40,000 women per year and enjoys a 70% compliance rate. Researchers compared digital versus conventional mammography in two groups with 14,385 patients each. Patients were matched by age and breast density and the participating radiologists and radiographers were identical for both cohorts.

The screening program's typical detection rate is 8.25% on initial screens and 3.45% on repeat screens. In this study, most of the mammograms were repeat exams.

FFDM had a higher recall rate (4.29% versus 3.46%) for radiological abnormalities but a lower recall rate for technical quality problems (.27% versus .50%) compared to conventional mammography.

In total, 657 (4.56%) patients were recalled based on digital studies versus 570 (3.96%) based on screen-film mammography exams.

Digital picked up 105 cancers versus 84 for screen-film. Most of the additional cancers were low grade and of intermediate suspicion. Digital also identified more microcalcifications in dense breasts.

In another study presented in the same session, researchers were highly encouraged by FFDM performance, noting that "digital mammography will be the leading modality in mammography screening in the future."

In that study, researchers at the University of North Norway assessed results in the Norwegian Breast Cancer Screening program for women aged 50 to 69. Almost 5000 women received digital mammography versus about 12,000 who received for screen-film mammography.

The recall rate in the study was higher for digital, at 2.6% versus 1.9% for screen-film. The number of cancers detected per woman screened rose to 6.3 per 1000 with digital, compared with 3.6 per 1000 with screen-film mammography. Tumor size and grade did not differ significantly.

"Digital mammography had a lower average radiation dose relative to screen-film mammography and tended to have higher recall and detection rates," said Solveig Hofvind, who presented results.

"Digital mammography can safely be used in a population-based screening program," she said.

In a third paper presented at the RSNA meeting, researchers analyzed data for 24,000 women who were part of the Oslo II randomized screening study, including 17,000 who underwent screen-film mammography and 7000 on FFDM. Out of 105 cancers detected, 64 were diagnosed on screen-film and 41 on FFDM.

The FFDM recall rate was 4.2% versus 2.5% for screen-film. Researchers also analyzed radiologist readers and found no significant differences.