Just like any other kind of interpretation, reading a mammogram is a skill that radiologists develop over time. They look for any signs of abnormality, including:
- asymmetries (something on one side that's not on the other)
- irregular areas of increased density
- clusters of small calcifications
- any area of skin thickening
In the United Kingdom, two radiologists independently read each screening mammogram. The radiologists look at mammograms in batches of about 35 mammograms. Other studies have suggested that the accuracy of the radiologists goes down over time, so the mammograms read last may be read less accurately than the mammograms read first.
To get more information, a study changed the order in which the second radiologist read a batch of screening mammograms. The results suggests that the accuracy of mammogram readings doesn’t go down over time and changing the order of a second reading doesn’t improve accuracy.
The study was published in the May 10, 2016 issue of JAMA. Read the abstract of “Effect of Using the Same vs Different Order for Second Readings of Screening Mammograms on Rates of Breast Cancer Detection: A Randomized Clinical Trial.”
The large study involved 46 breast screening centers in England. From December 2012 and November 2014, about 1.2 million women had screening mammograms that were read by 368 experts who were all fully qualified to read mammograms:
- 186 radiologists
- 143 radiography advanced practitioners
- 31 breast clinicians
The mammogram readers were randomly split into two groups:
- one group read the mammograms in the same order (597,505 mammograms)
- one group read the mammograms in the opposite order (596,642 mammograms)
Each mammogram reader looked at 176 batches of mammograms and each batch included about 35 mammograms.
After any follow-up diagnostic tests were done, 10,484 cases of breast cancer were detected overall:
- 5,272 cancers were detected in the mammograms read in opposite order (0.88% incidence rate)
- 5,212 cancers were detected in the mammograms read in the same order (0.87% incidence rate)
So changing the order in which the mammograms were read didn’t improve the detection rate, suggesting that the accuracy of mammogram reading doesn’t go down over time.
The study also found that there were no differences in:
- the rate of women called back for more testing (4.14% in the same order group vs. 4.17% in the opposite order group)
- the rate of disagreements between readers (3.43% in the same order group vs. 3.48% in the opposite order group)
The researchers that did the study wrote: "[Changing the order in which the mammograms were read] did not influence cancer detection rate, recall rate, or rate of disagreement between readers. There was no pattern of decreasing cancer detection rate with time on task as predicted by previous research on vigilance decrements as a psychological phenomenon."
"We found no reduction in performance or vigilance decrement at all," said Sian Taylor-Phillips, Ph.D., of the University of Warwick Medical School and first author of the study. "In fact, we found the opposite of what we were expecting -- breast screening readers seemed to get 'into the zone' and their performance improved with time on task. They recalled fewer women for further tests as they got nearer the end of the batch while cancer detection rates stayed constant."
The results of this study are very encouraging. If you have any worries about the accuracy of your mammogram reading, these findings should ease them.
If you're 40 or older and have an average risk of breast cancer, yearly screening mammograms should be part of your healthcare. If your breast cancer risk is higher than average, you should talk to your doctor about a more aggressive breast cancer screening plan that makes the most sense for your particular situation.
There's only one of you and you deserve the best care possible. Don't let any obstacles get in the way of your regular screening mammograms:
- If you're worried about cost, talk to your doctor, a local hospital social worker, or staff members at a mammogram center. Ask about free programs in your area.
- If you're having problems scheduling a mammogram, call the National Cancer Institute (800-4-CANCER) or the American College of Radiology (800-227-5463) to find certified mammogram providers near you.
- If you find mammograms painful, ask the mammography center staff members how the experience can be as easy and as comfortable as possible for you.
For more information, visit the Breastcancer.org Mammograms pages.