AJR: Digital mammo use increases cancer detection rate

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An increase in the cancer detection rate occurred initially during the conversion from film-screen to digital mammography, which subsequently decreased but remained higher than before digital conversion, according to a study of a community-based mammography practice in the August issue of the American Journal of Roentgenology.

Fred S. Vernacchia, MD, from the San Luis Diagnostic Center in San Luis Obispo, Calif., and colleagues undertook the retrospective evaluation of the impact on recall rates and cancer detection when converting from film-screen to digital mammography in a community-based radiology practice.

The researchers compiled audits of an institution's records during a four-year period: the year before conversion to digital mammography (Audit One) and the first, second and third years after conversion (Audits Two, Three and Four, respectively). They found that 4,838 film-screenings were performed during the period of Audit One without the use of the digital system; 6,875 screenings were performed using the digital system during Audit Two; 7,379 screenings during Audit Three; and 7,294 during Audit Four. They determined the cancer detection and recall rates for each audit.

The investigators found that cancer detection rates increased from 4.1/1,000 during film-screenings to 7.9/1,000 the year after the introduction of digital mammography. They found that the recall rates also increased the year after digital mammography was introduced, from 6.1 percent to 10.2 percent. Audit Three showed no statistically significant difference in cancer detection rates from those in Audit One, decreasing to 5.1/1,000. However, Audit Four noted an increase in the cancer detection rate to 6.9/1,000.

Vernacchia and colleagues concluded that their study findings suggest that new technology alone is responsible for the increased number of cancers detected in patients with dense breasts that were not previously found using film-screening.

The authors observed that a slightly higher cancer detection rate could be attributed to a high percentage of patients with dense breasts, or an influx of patients with dense breasts or an influx of other high-risk patients (e.g., 40- to 50-year-old women or premenopausal women). However, they acknowledged that they "do not have the statistics to support this premise."