A recent survey of over 2,000 women newly diagnosed with breast cancer found that half of those who undergo bilateral mastectomy after genetic testing don’t actually have mutations known to confer increased risk of additional cancers, according to a study led by University of Michigan Comprehensive Cancer Center researchers.

Instead the women had what are known as variants of uncertain significance, or VUS, that are often eventually found to be harmless. A bilateral mastectomy is a surgical procedure in which both of a woman’s breasts are removed after a diagnosis of cancer in one breast.

The finding highlights the need for genetic counselors to help both patients and physicians better understand the results of genetic testing intended to determine a woman’s risk for cancer recurrence or for developing a separate cancer in her ovaries or unaffected breast.

“Our findings suggest a limited understanding among physicians and patients of the meaning of genetic testing results,” says lead study author Allison Kurian, MD, associate professor of medicine and of health research and policy at Stanford University School of Medicine.

“Clinical practice guidelines state that variants of uncertain significance should not be considered to confer high cancer risk, and that patients with these variants should be counseled similarly to a patient whose genetic test is normal,” she adds. “However, many of the physicians surveyed in our study stated that they manage these patients in the same way as they do patients with mutations known to increase a woman’s risk.”

Only about half of the surveyed women who received genetic testing ever discussed their test results with a genetic counselor, and between one–quarter and one–half of the surveyed breast cancer surgeons indicated they treat women with VUS no differently than women with known cancer–associated mutations, the researchers found. Furthermore, some women undergo surgery prior to receiving genetic testing or seeing the results.

The study was published in the Journal of Clinical Oncology.

In this study, the researchers asked 2,502 women newly diagnosed with breast cancer whether they had received genetic testing, and if so, whether the testing and any discussion of results occurred before or after breast surgery.

They found that of the 666 women who had received testing, 59 percent were considered to have a high risk of a dangerous mutation in a cancer–associated gene. About one–quarter of these women had genetic testing only after surgery — meaning critical decisions were made about their care before information about their mutation status was available. Delays in testing were particularly pronounced in women who lacked private health insurance.

The researchers then polled the surgeons who treated the women in the survey. They found that, when compared with doctors who had treated 51 or more newly diagnosed breast cancer patients during the previous year, doctors who had treated fewer than 21 breast cancer patients were: less confident in discussing the results of genetic testing with patients, more likely to order the genetic test without referring women to a genetic counselor, less likely to delay surgery in order to have test results available for surgical decision–making and more likely to manage a patient with variants of uncertain significance in the same way they would manage patients with proven high–risk mutations in cancer–associated genes.