The typical follow-up for a mammogram read as ‘probably benign,’ repeat testing in 3 to 6 months may be excessive, according to an article in the March 19th issue of the Journal of the National Cancer Institute.

Researchers examined the mammography records of nearly 60,000 women enrolled in the Women's Health Initiative project, one of the largest preventive health studies in the United States. Among the women who had ‘probably benign’ mammogram results, only 1 percent were diagnosed with breast cancer within the following 2 years.

"This result suggests that the current recommendation -- repeat mammography within 6 months -- should be reconsidered," said Shagufta Yasmeen, M.D., lead author of the study. "Going in for a repeat mammogram involves significant psychological trauma, expense and inconvenience, and can lead to unnecessary biopsies and other tests. Our study suggests this recommendation may be given too often, and may not be necessary in some cases. One-year follow-up may be more appropriate for most of these women."

All radiologists in the United States now use the American College of Radiology Breast Imaging Reporting and Data System to classify and report mammography findings. The college divides mammograms into 5 assessment groups ranging from category 1 (negative) to category 5 (highly suggestive of malignancy), and it has specific follow-up recommendations for each group.

For category 3 (probably benign) findings, the recommendation is for follow-up testing every 3 to 6 months until the radiologist determines such frequent follow-up is no longer necessary -- usually because the abnormality has not changed in size or appearance. However, there is limited evidence to support the category 3 recommendation, and researchers have started to question whether the frequent follow-up is necessary.

The researchers examined the incidence of breast cancer among 58,408 postmenopausal women who underwent screening mammograms at 40 centers around the country as part of the Women's Health Initiative. Overall, 5.2 percent -- or 2,927 -- of the women in the study had probably benign mammogram results. After 2 years, 1 percent of these women developed breast cancer compared with 0.6 percent of women with benign mammograms and 0.5 percent of those with negative mammograms.

The new study also raises questions about whether the Breast Imaging Reporting and Data System (known as BI-RADS) is being used to full advantage. Roughly 5 percent of all mammograms in the study were classified as probably benign, several times the expected rate of 1.2 percent.

In an accompanying editorial, researchers suggested 2 possible reasons for the high rate: "One explanation for this finding is that radiologists did not use the BI-RADS 3 assessment category as intended by the American College of Radiology," the editorial stated. "An alternative explanation is that comparison films may not have been readily available for a substantial portion of women undergoing screening mammography, which may have resulted in unnecessary surveillance of probably benign lesions."

Probably benign assessments are intended for use when interpreting a woman's first screening mammogram or a subsequent mammogram when her previous films are not available for comparison. When a previous mammogram is available for review, the comparison film can be used to determine whether a lesion is stable, decreasing in size, or growing. If the comparison film establishes that a lesion is not growing, a woman does not need any special follow-up.

"This is a key message for women," said Patrick Romano, M.D., a coauthor of the new study. "Mammograms are not like flu shots -- women should always try to go where they have gone before, or else obtain copies of their prior films when they switch to a new mammography center. Women and their referring physicians should ensure that previous films are available for comparison, to minimize unnecessary surveillance of benign lesions."