Breast biopsies are good at telling the difference between healthy tissue and cancer, but less reliable for identifying more subtle abnormalities, The New York Times reports that a new study finds. Because of the uncertainty, women whose results fall into the gray zone between normal and malignant – with diagnoses like "atypia" or "ductal carcinoma in situ (DCIS)" – should seek second opinions on their biopsies, researchers say in the report. Misinterpretation can lead women to have surgery and other treatments they do not need, or to miss out on treatments they do need.
The new findings challenge the common belief that a biopsy is the gold standard and will resolve any questions that might arise from an unclear mammogram or ultrasound. In the US, about 1.6m women a year have breast biopsies; about 20% of the tests find cancer and 10% identify atypia, a finding that cells inside breast ducts are abnormal but not cancerous. About 60,000 women each year are found to have DCIS, which also refers to abnormal cells that are confined inside the milk ducts and so are not considered invasive; experts disagree about whether DCIS is cancer.
"It is often thought that getting the biopsy will give definitive answers, but our study says maybe it won't," said Dr Joann G Elmore, a professor at the University of Washington School of Medicine in Seattle and the first author of the new study on the accuracy of breast biopsies.
Her team asked pathologists to examine biopsy slides, then compared their diagnoses with those given by a panel of leading experts who had seen the same slides. There were some important differences, especially in the gray zone. In Elmore’s study, the panel of three expert pathologists examined biopsy slides from 240 women, one slide per case, and came to a consensus about the diagnosis. Then the slides were divided into four sets, and 60 slides were sent to each of 115 pathologists in eight states who routinely read breast biopsies. The doctors interpreted the slides and returned them, and the same set was sent to the next pathologist. The study took seven years to complete.
The goal was to find out how the practicing pathologists stacked up against the experts. The task was tougher than actual practice, because in real cases pathologists can consult colleagues about ambiguous findings and ask for additional slides. They could not do so in the study. There was good news and bad news. When it came to invasive cancer – cancer that has begun growing beyond the layer of tissue in which it started, into nearby healthy tissue – the outside pathologists agreed with the experts in 96% of the interpretations, which Elmore called reassuring. They found the vast majority of the cancers. For completely benign findings, the outside pathologists matched the experts in 87% of the readings, but misdiagnosed 13% of healthy ones as abnormal.
The next two categories occupied the gray zone. One was DCIS – for this condition, the pathologists agreed with the experts on 84% of the cases. But they missed 13% of cases that the experts had found, and diagnosed DCIS in 3% of the readings where the experts had ruled it out.
The finding is of concern, because DCIS sometimes becomes invasive cancer, and it is often treated like an early-stage cancer, with surgery and radiation. Missing the diagnosis can leave a woman at increased risk for cancer – but calling something DCIS when it is not can result in needless tests and treatments.
The second finding in the gray zone was atypia, in which abnormal, but not cancerous, cells are found in breast ducts. Women with atypia have an increased risk of breast cancer, and some researchers recommend surgery to remove the abnormal tissue, as well as intensified screening and drugs to lower the risk of breast cancer. But in the study, the outside pathologists and the experts agreed on atypia in only 48% of the interpretations. The outside pathologists diagnosed atypia in 17% of the readings where the experts had not, and missed it in 35% where the experts saw it. "Women with atypia and DCIS need to stop and realise it's not the same thing as invasive cancer, and they have time to stop and reflect and think about it, and ask for a second opinion," Elmore said.
A JAMA editorial called the findings "disconcerting." It said the study should be a call to action for pathologists and breast cancer scientists to improve the accuracy of biopsy readings, by consulting with one another more often on challenging cases and by creating clearer definitions for various abnormalities so that diagnoses will be more consistent and precise. The editorial also recommended second opinions in ambiguous cases.
[link url="http://www.nytimes.com/2015/03/18/health/breast-biopsies-dcis-atypia-diagnosis-leave-room-for-doubt.html?&moduleDetail=top-news-2&action=click&contentCollection=N.Y.%20%2F%20Region®ion=Footer&module=TopNews&pgtype=article&_r=0"]Full report in The New York Times[/link]
[link url="http://jama.jamanetwork.com/article.aspx?articleid=2203798"]JAMA abstract[/link]
[link url="http://jama.jamanetwork.com/article.aspx?articleid=2203783"]JAMA editorial[/link]