by Carol Ko
, Staff Writer | July 19, 2013
From the July 2013 issue of HealthCare Business News magazine
Just now common are false positives? It depends on your definition. More than half of women who get mammograms in their forties can expect to get called back for additional screenings, though many doctors dispute whether this should count as a false positive.
It’s estimated that 7 to 9 percent of patients will receive a false-positive biopsy recommendation, while false positive results will send 10 out of 200 women to unnecessary surgery.
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“One of the things about the risks of screening is patients get unnecessary biopsies and callbacks — better precision in imaging would help that,” says Dr. Julia White, professor of oncology at Ohio State University.
But there’s a tricky balance between lowering false positives while maintaining enough screening accuracy to avoid an uptick in false negatives. The challenge for screening technology is essentially twofold: screenings must be accurate enough to pick up on abnormalities while being sensitive enough to rule out misleading signs.
On the lab-error side, manufacturers have also devised products to help remedy the problem on a more practical level. The Know Error System, for example, is a DNA matching product that confirms that surgical biopsy samples being evaluated belong to the patient being diagnosed. Such safeguards may help put patients’ worries to rest as they go into surgery.
Dr. David Dorfman of Zwanger-Pesiri Radiology in New York says that the product has helped greatly enhance patient satisfaction at relatively low cost.
Along with the question of false positives, there’s also uncertainty around the issue of overtreatment. A one-size-fits-all treatment may be unnecessary, even outright harmful, depending on the kind of breast cancer screenings detect, according to experts. “Breast cancer is a very heterogeneous disease and has different risks and recurrence rates,” says Dr. John Nelson of Battlefield Imaging.
For example, a screening may turn up abnormalities such as DCIS—a kind of slow-growing cancer in the breast duct that usually never progresses to the point of killing a woman. If such abnormalities are found, it’s followed up with more tests, and if it’s found to be cancerous — even if it’s relatively harmless — women commonly have it treated with radiation, hormone therapy, chemotherapy, surgery, or even breast removal, all of which pose additional risks that may not be worth it if the cancer poses little mortality risk for the patient.
One of the major limitations of mammography lies in its failure to adequately detect cancer in women with dense breasts, or breasts that have more connective tissue than fatty tissue. Approximately 40 percent of patients undergoing screenings have dense breasts.