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• Posted July 19, 2024

Current Gene Screens Miss Many at High Cancer Risk: Study

As good as many genetic tests might be, a deeper look at the DNA of over 44,000 people identified many who carried genes that hike their risks for cancer, researchers said.

"This study is a wake-up call, showing us that current national guidelines for genetic screenings are missing too many people at high risk of cancer," said lead author Dr. Niloy Jewel Samadder. He's a Mayo Clinic gastroenterologist and cancer geneticist at the Center for Individualized Medicine and the Mayo Clinic Comprehensive Cancer Center.

"Early detection of genetic markers for these conditions can lead to proactive screenings and targeted therapies, potentially saving lives of people and their family members," Samadder said in a Mayo Clinic news release.

The study is part of the Tapestry project at the Mayo Clinic's Center for Individualized Medicine. This research initiative goes beyond the genome to look at each patient's exome -- the protein-coding regions of individual genes.

The project has already sequenced the exomes of more than 100,000 patients, Mayo noted in a news release.

In the latest study, Samadder and his colleagues focused on the exome because it is the most likely area for mutations that give rise to disease.

They looked at the exomes of over 44,000 people of varying backgrounds and found that 550 of them -- about 1.24% -- did carry a hereditary genetic mutation that upped their odds for either breast and/or ovarian cancers or Lynch syndrome, a condition that raises the odds for endometrial and colorectal cancers.

More than half of the people identified as carrying these mutations previously had no idea they were were at risk, and 40% would not have even met the criteria for genetic testing, the authors noted.

Mutations in the BRCA1 and BRCA2 genes have long been known to raise a person's odds for breast and ovarian cancers. As Samadder's team noted, carrying BRCA1 confers a 60% lifetime risk of developing breast cancer and a 40% risk of getting ovarian cancer.

BRCA2 mutations confer a lifetime risk of developing breast cancer of 50% and ovarian cancer of 20%, with additional risks for prostate and pancreatic cancers in men. 

Having Lynch syndrome confers an 80% lifetime risk of developing colorectal cancer and 50% risk of uterine/endometrial cancers.

The findings were published July 16 in the journal JCO Precision Oncology.

According to the researchers, minority groups may especially miss out when it comes to screening for genes that raise cancer risks.

"Existing guidelines for genetic testing inadvertently introduce biases that affect who qualifies for testing and who receives coverage through health insurance," Samadder said. "Our results emphasize the importance of expanding genetic screening to identify people at risk for these cancer predisposition syndromes."   

More information

Find out more about gene tests for cancer at the U.S. National Cancer Institute.

SOURCE: Mayo Clinic, news release, July 16, 2024