According to the results of a study published in the Journal of the National Cancer Institute, the accuracy of diagnostic mammograms varies widely across radiologists; this variability is not explained by patient characteristics.
A mammogram is an X-ray image of the breast that can reveal irregularities and help to detect cancer early when it is most treatable. A screening mammogram is a mammogram performed on a woman with no signs or symptoms of breast cancer. A diagnostic mammogram is a mammogram performed to evaluate a breast problem.
The accuracy of both types of mammograms is very important. False-positive results expose women to unnecessary anxiety and follow-up tests. False-negative results delay the diagnosis of breast cancer.
The accuracy of screening mammograms has been shown to vary widely, but less is known about the accuracy of diagnostic mammograms. To explore the accuracy of diagnostic mammograms, researchers conducted a study among 123 radiologists who had interpreted 35,895 diagnostic mammograms.
The study assessed both the sensitivity of the diagnostic mammograms and the false-positive rate. Sensitivity refers to the completeness with which the diagnostic mammograms identified breast cancer. In other words, out of all the women with breast cancer, what proportion had a positive diagnostic mammogram? The false-positive rate assesses the frequency of positive mammograms among women who don’t have cancer.
- Across radiologists sensitivity ranged from 27% to 100% (median was 79%).
- The false-positive rate ranged from 0% to 16% (median was 4.3%).
- Radiologists at academic medical centers had higher sensitivity (88%) than other radiologists (76%). Radiologists at academic medical centers also had higher false-positive rates (7.8% versus 4.2%).
- Radiologists who spent 20% or more of their time on breast imaging had higher sensitivity (80%) than radiologists who spent less time on breast imaging (70%). The false-positive rate was only slightly higher among radiologists who spent more time on breast imaging (4.6% versus 3.9%).
- More recent training in radiology and more experience performing breast biopsies results were also linked with greater sensitivity and a higher false-positive rate.
- This variability across radiologists was not explained by differences in patient characteristics.
The researchers conclude that the accuracy of diagnostic mammograms varies across radiologists. The researchers note: “This variability is concerning and likely affects many women with and without breast cancer.”
Reference: Miglioretti DL, Smith-Bindman R, Abraham L et al. Radiologist characteristics associated with interpretive performance of diagnostic mammography. Journal of the National Cancer Institute. 2007;99:1854-63.