Long-running debate
The new findings and opinions add to a long-running debate in oncology over the role of genetic testing and screening for pathogenic mutations.
Part of the debate about genetic testing has hinged on the question of costs, said Dr. Beitsch. When genetic testing first became available, it was conducted by hand, and costs were often prohibitive. Since then, genetic testing has been automated using next-generation sequencing, and the cost has decreased considerably.
“The Invitae cash price for an 80-plus gene panel is $250. That’s [the cost of] a mani-pedi in Dallas. I don’t discount that it’s a lot of money for a lot of people. Yes, it’s expensive, but it’s a lot less expensive than it used to be,” Dr. Beitsch said.
Another issue is that doctors are not entirely sure how to manage variants of uncertain significance (VUSs) when they are found. In the Mayo Clinic study, about half (47.4%; n = 1415) of participants had VUSs. The authors noted that these results are consistent with past studies.
Dr. Beitsch said that VUSs are a matter of education. To date, only about 2% of VUSs have been associated with cancer. The remainder, about 98%, do not affect treatment for patients who have already been diagnosed with cancer.
“We all have VUSs. They’re just minor variations in a gene. The vast majority of them have no consequence and don’t alter the function of the gene,” he said. “I tell everybody to ignore the VUSs [when found in patients with cancer]. Do not act on them at all. We just need to educate everybody to make sure they don’t get stressed about it.”
These comments echo guidance from the American Society of Breast Surgeons, which says that VUSs are DNA sequences that are not clinically actionable. This type of result needs to be considered as inconclusive, and patient management should not be influenced by such results.
However, VUSs are more significant if they are found in individuals who do not have cancer but who have a strong family history of cancer. In such cases, clinicians should be more aware, Dr. Beitsch emphasized.
“Patients who have a VUS and don’t have a cancer should absolutely pay more attention to their health. They got tested for a reason, and that reason is usually strong family history,” Dr. Beitsch said.
He added that a major advantage of genetic testing is that it can enable cascade genetic testing of family members. Identifying pathogenic mutations in family members can lead them to undergo screening to detect early cancers, and preventive measures can be taken that may be lifesaving.
In the Mayo Clinic study, researchers offered genetic testing to family members of patients who tested positive for a pathogenic mutation. Testing was available free of charge for up to 90 days after a participant tested positive. In addition, family members were shown an educational video.
Nevertheless, only 17.6% (n = 70) of patients with pathogenic mutations had family members who underwent testing. Among these, 45% (79 of 176) of family members who were tested were found to carry pathogenic mutations.
“This really told us that financial barriers are not the only barrier to families understanding and undergoing preventive testing,” Dr. Samadder said. “There are probably a number of other barriers – socioeconomic or emotional – that we have to deal with.”
Genetic testing was provided by Invitae. The study was supported by several grants, including a Mayo Transform the Practice Grant, and by Mayo Clinic’s Center for Individualized Medicine. Two coauthors are employees of Invitae. Dr. Beitsch reported participating in a study 2 years ago that was funded by Invitae. He currently receives no financial support from Invitae. Several authors report receiving fees from one or more of the following companies: Pfizer, Maze Therapeutics, Genome Medical, Astellas, and Merck.
This article first appeared on Medscape.com.