Oslo study finds digital imaging comparable to film in breast cancer detection

Full-field digital mammography is comparable to screen-film in detecting breast cancer, according to results of a randomized trial in Norway involving nearly 25,000 women.

The findings presented during a scientific session at the RSNA meeting mark the final report from the Oslo I and II trials, which compared the two technologies in 24,908 women who received initial scans and were then followed for two years. All digital mammograms were read in soft-copy format.

A team led by Dr. Per Skaane at Ullevaal University Hospital in Oslo evaluated recall rates, positive predictive values, and cancer detection rates in women in two age groups: 45 to 49, and 50 to 69. Preliminary findings were reported in the July issue of Radiology (2004;232:197-204).

Full-field digital mammography did detect more cancers than screen-film, but the difference was not statistically significant, Skaane said, in part due to the technique's higher recall rates. Positive predictive values for both technologies were comparable.

In the 50 to 69 age group, for example, there was only borderline significance to FFDM's higher cancer detection rate. In the 45 to 49 age group, the difference in cancer detection rates of 33% and 24% for digital and screen film, respectively, was not statistically significant.

"This follow-up to the Oslo II study confirms our initial results, that cancer detection rates are higher for digital mammography as compared with screen-film," Skaane said. "But this higher rate may be partly explained by a higher recall rate. Overall, and as was our purpose, we have established that full-field digital mammography is comparable to film for screening programs."

The Oslo study is one of a trio of trials to determine clinical differences between digital mammography and screen-film. The first, published by Dr. John Lewin in 2002, also reported no observable differences in cancer detection rates between the two techniques but did find that digital led to fewer recalls than screen-film.

Results from a third study, the Digital Mammography Imaging Screening Trial, are expected to be published in spring 2005. The trial involves 29,538 women at 35 medical centers across the U.S.