Ability To Read Mammograms Varies Widely

April 20, 1998

The mammogram-reading skills of general radiologists vary enormously according to a study to be presented Monday, April 20, at the 28th National Conference on Breast Cancer in Washington, DC. Although the researchers who performed the research were impressed with the overall ability of most general radiologists, they were troubled by the magnitude of the variance.

Seventy-five general radiologists detected, on average, 70 percent of 50 breast cancers visible on 100 mammograms, about what previous studies would predict. Three expert mammographers detected 81 percent. All the experts all had similar scores, ranging from 76 percent to 86 percent. For the generalists, however, scores ranged from a high of 98 percent -- with a lot of false positives (normal exams rated as cancerous) -- to a low of eight percent.

"The generalists' scores were all over the map," said Robert Schmidt, M.D., associate professor of radiology at the University of Chicago and director of the study, "rather than clustered around 70 percent. The average score was no surprise. Most previous studies suggest that 15 to 30 percent of cancers are not detected at the first opportunity. But the extreme range was an eye opener."

Moreover, there was only a weak correlation between the test results for each generalist and his or her self-assessed level of expertise. For example, some of those who classified themselves as having advanced skills, scored lower than those who rated themselves as novices.

"Imaging technology has steadily improved and continues to get better," said Schmidt. "Now, the human observer may often be the weakest link in the breast-imaging chain."

Most quality-of-care research is performed at academic centers and focuses of the talents of highly specialized experts who devote their careers to a few specific interests, such as mammography.

The majority of screening mammograms, however, are read by general radiologists, who may read as few as two mammograms a day.

The researchers -- from the University of Chicago, New York University, University of New Mexico at Albuquerque, and University of Illinois at Peoria -- presented high-quality films from 100 mammography cases to 100 radiologists who were attending continuing medical education meetings, and to four mammography experts.

Each radiologist was given two-and-one-half hours to complete the exercise, conditions roughly comparable to a routine clinical situation, except for the higher percentage of cancers. Ordinarily, there is only about one cancer per 1,000 screening mammograms.

The 100 films contained 55 normal cases and 45 cases with at least one cancer. (Five cases had two cancers). The observers were asked to rate the cases as normal or abnormal and to indicate the location of a lesion. The cancers were typical lesions found by routine screening mammograms, not unusually difficult or "tricky" cases.

Only 75 percent of each group of radiologists finished the task. Those who completed fewer than 90 of the 100 cases were not included in the final assessment, "but they clearly would not have improved the scores," noted Schmidt. Those who did not complete the test found only 42 percent of the cancers in the cases they completed.

The experts detected 16 percent more cancers than generalists. Experts, however, were slightly more likely to rate normal cases as abnormal.

"Dedicated mammographers seemed to have a lower threshold for what they find suspicious than generalists," said Schmidt. "They found significantly more cancers but wanted to take a closer look at more women who did not have cancers."

Although the 70-percent detection rate may seem low, "reading mammograms is extremely difficult, even for the experts," cautioned Schmidt. It requires a lot of training and experience. "Very few people who don't do it full-time develop the skills to do it at the highest levels."

That's because reading screening mammograms is very different from other tasks performed by radiologists. Instead of looking for the cause of symptoms in a sick person, screening studies look for signs of minute, pre-symptomatic disease in healthy patients. It requires a different mind-set, says Schmidt, and different sets of behaviors.

"The good news," added Schmidt, "is that this is a problem we know how to solve. We can teach generalists to read these images consistently and with a level of accuracy level closer to that of the experts. But we need to develop methods to make this training more accessible to all radiologists."

On one case, 85 percent of the generalists missed a cancer found by 100 percent of the experts. "As you might expect, we now use that as a teaching case," emphasized Schmidt.

Ongoing technology improvements will also help. Digital mammography units, which enable physicians to manipulate the images in new ways, are entering the market. And researchers at the University of Chicago have developed a computer that read mammograms, providing a second opinion for the radiologist and cutting the error rate.

Until these technical advances become more common, Schmidt recommends that women seek breast programs at academic institutions or specialized breast diagnostic centers with dedicated mammographers, who are more likely to have the advanced training and experience.

The American Cancer Society estimates that 178,700 women will be diagnosed with invasive breast cancer in the United States in 1998 and 43,900 women will die from the disease. About one in eight American women will develop the disease by age 85. Mammography is the only known method that can find small, curable cancers before they can be felt, and has been shown to significantly decrease deaths from breast cancer.
-end-


University of Chicago Medical Center

Related Breast Cancer Articles from Brightsurf:

Oncotarget: IGF2 expression in breast cancer tumors and in breast cancer cells
The Oncotarget authors propose that methylation of DVDMR represents a novel epigenetic biomarker that determines the levels of IGF2 protein expression in breast cancer.

Breast cancer: AI predicts which pre-malignant breast lesions will progress to advanced cancer
New research at Case Western Reserve University in Cleveland, Ohio, could help better determine which patients diagnosed with the pre-malignant breast cancer commonly as stage 0 are likely to progress to invasive breast cancer and therefore might benefit from additional therapy over and above surgery alone.

Partial breast irradiation effective treatment option for low-risk breast cancer
Partial breast irradiation produces similar long-term survival rates and risk for recurrence compared with whole breast irradiation for many women with low-risk, early stage breast cancer, according to new clinical data from a national clinical trial involving researchers from The Ohio State University Comprehensive Cancer Center - Arthur G.

Breast screening linked to 60 per cent lower risk of breast cancer death in first 10 years
Women who take part in breast screening have a significantly greater benefit from treatments than those who are not screened, according to a study of more than 50,000 women.

More clues revealed in link between normal breast changes and invasive breast cancer
A research team, led by investigators from Georgetown Lombardi Comprehensive Cancer Center, details how a natural and dramatic process -- changes in mammary glands to accommodate breastfeeding -- uses a molecular process believed to contribute to survival of pre-malignant breast cells.

Breast tissue tumor suppressor PTEN: A potential Achilles heel for breast cancer cells
A highly collaborative team of researchers at the Medical University of South Carolina and Ohio State University report in Nature Communications that they have identified a novel pathway for connective tissue PTEN in breast cancer cell response to radiotherapy.

Computers equal radiologists in assessing breast density and associated breast cancer risk
Automated breast-density evaluation was just as accurate in predicting women's risk of breast cancer, found and not found by mammography, as subjective evaluation done by radiologists, in a study led by researchers at UC San Francisco and Mayo Clinic.

Blood test can effectively rule out breast cancer, regardless of breast density
A new study published in PLOS ONE demonstrates that Videssa® Breast, a multi-protein biomarker blood test for breast cancer, is unaffected by breast density and can reliably rule out breast cancer in women with both dense and non-dense breast tissue.

Study shows influence of surgeons on likelihood of removal of healthy breast after breast cancer dia
Attending surgeons can have a strong influence on whether a patient undergoes contralateral prophylactic mastectomy after a diagnosis of breast cancer, according to a study published by JAMA Surgery.

Young breast cancer patients undergoing breast conserving surgery see improved prognosis
A new analysis indicates that breast cancer prognoses have improved over time in young women treated with breast conserving surgery.

Read More: Breast Cancer News and Breast Cancer Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.