Study: Prior mammograms make for more precise cancer detection

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Having access to prior mammograms can significantly boost a radiologist’s chances in detecting disease in current mammography studies and also may decrease unnecessary recalls by up to 44 percent, according to a study in the January issue of Radiology.

"Prior mammograms should always be used when available," said the study's lead author, Antonius A. J. Roelofs, PhD, from the Department of Radiology, Radboud University Nijmegen Medical Center in the Netherlands. "Limiting the availability of prior mammograms to cases selected by the reading radiologist appears to significantly reduce the beneficial effect shown when using prior mammograms in all possible cases," he said.

And the current transition from film mammography to digital mammography also poses technological hurdles. "Generally, diagnosis is based on the most recent mammograms and on prior screening round images," said co-author Sander van Woudenberg, MS. "The use of prior mammograms recorded on film in comparison with current digital mammograms poses a challenge, as reading digital images in combination with film images is difficult and may lead to loss of efficiency."

One solution – admittedly a painstaking one according to the authors – is to digitize all prior film mammograms. Another possible solution would involve limiting the number of prior mammograms used, the authors said.

For this study, twelve radiologists studied 160 mammograms to determine in retrospect the influence of comparing current mammograms with prior mammograms on breast cancer detection in screening. Also, the researchers sought to investigate a protocol in which prior mammograms are viewed only when deemed necessary by the radiologist.

Eighty mammograms were obtained from women in whom breast cancer was diagnosed later. The other 80 mammograms had been reported as normal or benign. All cancers were visible in retrospect. The reviewers remained unaware of the pathologic nature of the lesions until the whole study was completed. Readers located abnormalities, estimated likelihood of malignancy for each finding and indicated whether prior mammograms were considered necessary.

According to the results, without the use of prior images many more suspicious findings were noted by the radiologists. Reading performance was significantly better when prior screening mammograms were available.

The radiologists reported 1,935 findings when prior mammograms were unavailable. When prior mammograms were available, 1,715 findings were reported. The total number of localized lesions detected without and with prior mammograms was 636 and 672, respectively.

The radiologists primarily used the prior mammograms for assessment and not as an important tool in the initial detection of abnormalities. Generally because there was additional information available from the prior mammograms, the radiologists were able to make better judgments which translated into 44 percent fewer nonmalignant findings as suspicious, resulting in a corresponding reduction in recall rates.

"Women should make sure that if they are moving to another place, their screening mammograms and files are moved as well," Roelofs said.