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False-positive mammograms may signal higher risk

Friday April 6, 2012
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False-positive mammograms potentially are an indicator of underlying pathology that could result in breast cancer, according to a study.

Screening mammography is associated with false-positive test results in disease-free women, and those women usually are referred back for routine screening after the initial diagnostic workup does not reveal cancer, researchers wrote in background information for the study, which appeared April 5 on the website of the Journal of the National Cancer Institute.

Suspicious findings on screenings that lead to false positives include asymmetric densities, skin thickening or retraction, tumor-like masses, recently retracted nipples and suspicious axillary lymph nodes. It has been unknown whether women whose mammographic screenings show these results have a higher long-term risk for breast cancer compared to women who initially test negative, the researchers wrote.

To determine whether women who test false-positive after mammography screenings have a higher risk of developing breast cancer than those who test negative, My von Euler-Chelpin, PhD, of the Department of Public Health at the University of Copenhagen, and colleagues gathered data from a long-standing population-based screening mammography program in Copenhagen, Denmark, from 1991 to 2005. They evaluated the risk of breast cancer and ductal carcinoma in situ in women who had received false-positive test results between ages 50 and 69. They compared the age-adjusted relative risk of breast cancer for women who had tested false-positive for breast cancer with that of women who had tested negative.

The researchers found that women who had tested negative for breast cancer had an absolute cancer rate of 339 per 100,000 person-years at risk, compared with 583 per 100,000 person-years at risk for women who tested false-positive. Even six years or more after the test, the higher relative risk of breast cancer in women with false-positive tests remained statistically significant compared with women who tested negative.

However, the researchers cautioned, "the excess breast cancer risk in women with false-positive tests may be attributable to misclassification of malignancies already present at the baseline assessment." Thus, new screening methods such as high-resolution ultrasound and stereotactic biopsy may result in more accurate diagnoses and fewer false positives on first screen.

The authors also cautioned that the experience of a false-positive might cause anxiety, which might discourage women from attending regular screenings. However, the long-term additional risk of breast cancer in women who tested false-positive underscores the need for women to have regular screenings: "Based on the findings in this study, it may be beneficial to actively encourage women with false-positive tests to continue to attend regular screening," the researchers wrote.

To view the study data and access the study via subscription or purchase, visit http://bit.ly/HhOUKO.

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