Assessing genetic cancer susceptibilities has traditionally involved targeted tests like BRCA1/2, followed by counseling and, sometimes, follow-up genetic testing and additional test-specific counseling.

Multigene panel technology that allows simultaneous testing of many genes, is gaining favor as a faster alternative—but these multiplex tests are outpacing the molecular-epidemiological evidence base and models for patient counseling, researchers warned Cancer Therapy Advisor.

New approaches are needed to help patients—and physicians—interpret and use multiplex test results.

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Multigene panel (“multiplex”) gene tests for cancer susceptibility can save time compared to sequential targeted-gene tests, and are becoming more widely used. Many see them as an inevitable and important step toward genomics-based cancer prevention.

But it is too soon for multiplex tests to be offered broadly as a routine part of cancer prevention efforts, cautioned Angela R. Bradbury, MD, assistant professor of Hematology/Oncology at the University of Pennsylvania Abramson Cancer Center in Philadelphia, PA.

“There are some patients who may benefit, but multiplex testing that includes moderate-penetrant genes is of unproven clinical utility and is not uniformly recommended by professional groups given the lack of data,” she said. “These issues are very complex and challenging and patients who elect for multiplex testing should understand these risks and limitations.”

Many companies offering panel tests and many physicians who order them emphasize their “potential” benefits with limited discussion of risk, Dr. Bradbury noted. She warned that this creates an impression among patients that “more is better” when it comes to genetic testing.

According to research from Dr. Bradbury and colleagues recently published in  Genetics in Medicine, when patients are offered pretest counseling that describes the limitations and risks, many choose to forego multiplex testing.1

A third of the study’s 49 patients, all of whom were at risk for breast cancer, opted out of multiplex testing or receiving test results, citing uncertainty and potential distress associated with results.1

“Our experience is that talking about the option to test for additional genes (in addition to BRCA1/2) is overwhelming,” Dr. Bradbury said.

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Pretest counseling helps identify patients who are “more likely to handle uncertainty and be less distressed with test results,” she said. It’s important to educate patients about the uncertainties and limitations of different testing strategies so that those who feel less tolerant of uncertainty, or who are more likely to feel test-associated distress, can opt out, she says.

Pretest counseling reduced general anxiety levels.1 Among the 33 patients who underwent multiplex testing and received results after counseling levels of anxiety, uncertainty, and depression did not increase significantly.1