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Universal gene tests better than targeted for cancer patients

JAMA Oncology
Reuters Health - 05/11/2020 - One in eight cancer patients carries a pathogenic germline variant (PGV), and in nearly 30% of these patients, the genetic findings may lead to treatment modification, according to new research.

"Close to 50% of these genetic mutations would not have been identified if clinicians followed guidelines," Dr. Jewel Samadder of Mayo Clinic in Phoenix, Arizona, the study's first author, told Reuters Health by phone.

Current guidelines on genetic testing for cancer patients are targeted and tumor-specific, Dr. Samadder noted. Not all clinicians follow them, he added, and the likelihood of cancer patients' having genetic testing vary based on where they are treated.

"All of these are issues with the current practice," he said. "Genetic testing is underutilized in cancer patients across America."

Genetic testing is especially vital in cancer care now, he added, when "we can actually use a genetic mutation to target the type of treatment to use."

Dr. Samadder and his team compared the prevalence of PGVs identified with universal testing to prevalence with targeted testing following National Comprehensive Cancer Network, National Society of Genetic Counselors, and American College of Medical Genetics guidelines. They looked at nearly 3,000 patients with solid-tumor cancers treated at Mayo Clinic cancer centers in Minnesota, Florida and Arizona, as well as a community oncology practice in Wisconsin.

Overall, 13.3% of patients had PGVs, including 282 cancer-susceptibility genes with moderate to high penetrance, the researchers report in JAMA Oncology. Among these patients, 192 (6.4%) would not have undergone testing based on phenotype or family history. Treatment was modified based on genetic findings in 28.2% of patients with high-penetrance PGVs.

Study participants' blood relatives were offered cascade family variant testing (FVT) at no cost. Just under 18% of the patients with PGVs had relatives who underwent FVT, 45% of whom had positive results.

About five years ago, Dr. Samadder noted, it cost thousands of dollars to test for a handful of cancer-susceptibility genes, but now it's possible to test for 80 to 100 genes for about $250. But while costs are lower, he added, barriers persist, including the fact that not all insurers will cover genetic testing for cancer patients and not everyone can afford to pay for it out of pocket.

"Any patient who has cancer should get genetic testing," Dr. Samadder added, noting that the Mayo Clinic has begun to implement universal genetic testing for cancer patients.

"We definitely don't want genetics to become a disparity in cancer care, or create a disparity," he concluded.

By Anne Harding

SOURCE: https://bit.ly/35YgtNb JAMA Oncology, online October 30, 2020.

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