Do patients and doctors understand breast cancer genetic testing results?

[April 20, 2017] By Will Boggs MD

(Reuters Health) - If you have early-stage breast cancer and have undergone genetic testing, the odds are high that the results were not explained to you by a genetic counselor, and chances are, the results did not affect your surgeon's recommendations for treatment, according to a recent U.S. study.

"Women should ask their clinicians to refer them to a genetic counselor to discuss their genetic testing results,” lead author Dr. Allison W. Kurian from Stanford University School of Medicine in California told Reuters Health. “Results of genetic testing are increasingly complex and difficult for those without genetics expertise to interpret correctly,” she said by email.

The added complexity is in part because more genes are being tested, which is good in that it increases the chance of finding a useful result, Kurian said. But it also increases the chance of finding an ambiguous “variant of uncertain significance (VUS),” she said.

Inherited mutations, sometimes called germline mutations, in the genes BRCA1 and BRCA2 are probably the best known as influencing a woman’s risk of breast and ovarian cancer. But these and other less well-studied inherited mutations can also influence her risk of cancer recurring or of a new cancer in the future, so they may indicate a need for different approaches to treatment.

Expert guidelines increasingly call for genetic testing to identify the presence of inherited mutations, particularly for women already diagnosed with breast cancer, the study team writes in Journal of Clinical Oncology. But it’s not clear if patients or their doctors are using the results to make informed treatment choices.

The researchers used information from two large registries, along with surveys of patients with early-stage breast cancer who had genetic testing and surveys of their surgeons, to examine patterns of genetic testing and counseling and the impact of test results on surgical decisions.

Out of 666 women who reported genetic testing, two-thirds were tested before they had surgery. Nearly three quarters of tested women had no mutation in BRCA1/BRCA2, while 7 percent did have a mutation in BRCA1/BRCA2 or another gene associated with breast cancer risk. Another 9 percent had a variant of uncertain significance.

Even though genetic counseling is recommended before genetic testing, only about 1 in 5 of the tests was ordered by a genetic counselor. Surgeons ordered the tests nearly half of the time and medical cancer specialists (oncologists) ordered about a third of the tests.

The researchers also divided women into high and average risk groups based on family history and other breast cancer risk factors to understand other possible influences on testing and treatment choices.

About half of women tested (57 percent of those at high risk of mutation based on other factors and 42 percent of those at average risk) discussed their results with genetic counselors. About 1 in 5 discussed their results only with their surgeons, and 17 percent in the higher risk group as well as 31 percent of those at average risk discussed their results only with their oncologists.

Higher-risk women were more likely to have bilateral mastectomy if testing found a high-risk mutation (80 percent), but many women underwent bilateral mastectomy even if they had a VUS (43 percent) or no mutation at all (34 percent). Bilateral mastectomy choices were similar among average-risk women.

Up to a third of surgeons rarely referred patients for genetic counseling and many surgeons said they never delayed surgery while waiting for genetic testing results.

Fewer than half of the surgeons surveyed said that they offered breast-conserving therapy to any women with mutations in BRCA1/BRCA2.

Half of the surgeons who treated a lower volume of breast cancer patients and one quarter of the surgeons with a higher volume of cases reported managing patients with VUS in the BRCA1/BRCA2 genes the same way as they managed patients with the well-established harmful mutations in BRCA1/BRCA2.

“This is concerning because practice guidelines explicitly state that VUS should not be treated in the same way as harmful mutations,” Kurian said. “In particular, the finding raises concern that misunderstanding of VUS (believing that they cause high cancer risk when they do not) may be responsible for unnecessary bilateral mastectomies,” she noted.

“It’s increasingly important that genetic tests be ordered and interpreted by genetic counseling experts,” she said.

SOURCE: http://bit.ly/2pCJSGG Journal of Clinical Oncology, online April 12, 2017.

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