Breast Cancer Genetic Testing Guidelines 'Simply Are Not Effective'

Kathy D. Miller, MD


April 18, 2019

This transcript has been edited for clarity.

Hi. It's Dr Kathy Miller from Indiana University. I want to return to a topic we've talked about before: genetic testing and the underuse of genetic testing in our patients and our population.

We talked about this before, when a study led by Mary-Claire King suggested that even if we used current testing guidelines 100% of the time, we would miss half of the families with BRCA1 or BRCA2 mutations.[1] That led to a call for population-based testing.

That study was a bit challenging for us because it was conducted in Israel in an Ashkenazi Jewish population, and many wondered whether perhaps in that population the risk was higher and that population-based testing might make more sense. But would that apply to a predominantly non-Ashkenazi Jewish, US-based population?

Well, now we have the results from a study led by a group in Texas, where they performed multigene panel testing in almost 1000 patients newly diagnosed with breast cancer.[2] About half of those patients met current testing guidelines based on family history, age, or disease phenotype, whereas about half did not.

The researchers found pathologic variants in one of the tested genes in approximately 9% of patients who met the testing guidelines and in approximately 8% of patients who did not meet the testing guidelines.

This is now the second study that suggests that the guidelines simply are not effective. The goal of the guidelines should be to have us testing patients who are more likely to have a mutation than patients who would not be recommended for testing. However, there was virtually no difference.

Think about this again. If knowing that genetic information might change a patient's treatment and what her family does about testing, risk-reducing surgery, early surveillance, or enhanced surveillance, are we really willing to leave half of those women, men, and families out of the ballgame without access to that knowledge?

Admittedly, there are many challenges when thinking about more widespread testing. First, there should be a strong recommendation that variants of unknown significance should not be reported to physicians or patients. A large amount of evidence demonstrates that they are misunderstood, misused, and considered to be pathologic when many of them are not.

To move toward more widespread testing, results should either be "we found an abnormality that we know causes harm" or "we did not find an abnormality that we know causes harm."

We also need to revisit when genetic testing should come into play. Perhaps it doesn't make sense for every patient to undergo genetic testing at the beginning of the process. Perhaps genetic testing should be offered to those patients who find an abnormality in their families.

There are many details to think about. But how many more studies need to suggest that the guidelines simply don't work before we will begin to have those discussions?

I would love your thoughts on this. I'll be back with you again soon.

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