Compare new and prior mammograms, doctors urge

By David Douglas

NEW YORK (Reuters Health) - Comparing a mammogram with previously obtained images greatly enhances the accuracy of evaluation, Dutch researchers report.

"In mammography screening," Dr. Antonius A. J. Roelofs told Reuters Health, "viewing current mammograms in association with prior mammograms ... may decrease the number of false alarms by as much as 44 percent."

Although such comparisons are made routinely with film-based screening, the transition to digital technology presents a number of problems in continuing the practice, Roelofs of Radboud University Nijmegen Medical Center and colleagues note in the journal Radiology.

To investigate how important viewing prior mammograms might be, twelve experienced screening radiologists used digital displays to read 160 screening mammograms twice -- once with and once without prior mammograms. Eighty of the mammograms were obtained from women who were later diagnosed with breast cancer, while the other 80 mammograms were from women with normal or benign results.

"When only positive cases were considered, no difference was observed," Roelofs' group reports. However, the number of possible lesions that proved to be non-lesions was reduced by 44 percent when prior screening mammograms were available.

A compromise approach was also tested, in which the reading radiologists asked for a prior film only when they felt it might be helpful. Roelofs said this strategy "appeared to reduce the large beneficial effect of prior mammograms significantly."

He said this "shows that radiologists cannot reliably predict for which current mammograms the prior mammograms are necessary," and concluded the study "proves the importance of prior mammograms in the reading process."

SOURCE: Radiology, January 2007.