Digital Mammography May Detect More Breast Cancers

Researchers from the San Luis Diagnostic Center in San Luis Obispo, California, have reported an increase in breast cancer detection with the change from film mammography to digital mammography screening. The details of this study appeared in the August 2009 issue of the American Journal of Roentgenology.[1] 

The accuracy of film mammography is limited in women under the age of 50 years due to increased breast density. Digital mammography produces images on a computer screen and can be enhanced or magnified to better detect lesions in the breast. Digital mammography should improve the accuracy of mammography in this age group, but studies so far have been equivocal. However, newer digital mammographic techniques can adjust the contrast of images, making it easier to detect abnormalities in dense breast areas. Researchers affiliated with the Digital Mammographic Imaging Screening Trial (DMIST) Investigators Group have reported that digital mammography is more accurate than film mammography in certain groups of women: those under the age of 50 years, those with dense breasts, and those who are pre- or perimenopausal. However, for the majority of women, the two techniques were equivalent. These researchers also reported that digital mammography was only cost-effective for women under 50 years of age and those with dense breasts up to age 65 years.

The current study was carried out in a small community-based radiology practice and compared the rate of breast cancer detection before and after conversion from film to digital mammography. They reported that the rate of breast cancer detection was 4.1/1,000 screenings with film (n=4,838). After the introduction of digital mammography, the rate of detection increased in the first year to 7.9/1,000 screenings (n=6,875). The recall rates increased form 6.1% to 10.2%, respectively. There were two more annual digital screening periods involving 7,379 patients in the second year and 7,294 patients in the third year. The detection rates were 5.1/1,000 for the second year and 6.9/1,000 for the third year. Recall rates were 6.4% and 9.3% for years two and three, respectively. These authors concluded that “the 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.”

Comments: Many radiology centers are changing from film to digital mammography, and there should be more data on the relative effectiveness of the two techniques. Digital mammography has the added advantages of easier storage and retrieval than film.

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