Germline genetic testing of cancer patients is rare despite practice guidelines recommending people get tested after receiving a diagnosis, according to a study published in JAMA.
Testing inherited DNA can enable genetically targeted treatment and can identify relatives who may benefit from cancer screening or actions to stop tumors from developing. The benefits have led the authors of practice guidelines to recommend that patients with ovarian, male breast, and pancreatic cancer undergo testing for inherited cancer susceptibility genes. Testing of female breast, prostate, and colorectal cancer patients is recommended in some circumstances as well.
To understand the extent to which physicians are following the guidelines, researchers at organizations including Stanford University and the University of Michigan analyzed registries in California and Georgia. The analysis covered 1.4 million patients diagnosed with cancer between 2013 and 2019 and tested through the end of March 2021.
In that dataset, 6.8% of patients underwent germline testing. The rate of testing was highest in male breast (50%), ovarian (38.6%), and female breast (26%). The testing rate in pancreatic cancer was 5.6%. Physicians at Memorial Sloan Kettering Cancer Center commented on the findings in an accompanying editorial.
“Genetic cancer susceptibility testing is underused, and this is a missed opportunity to decrease the population-level burden of cancer,” the physicians wrote. “With greater emphasis on overcoming both health system and patient-level barriers to genetic cancer susceptibility testing for patients with cancer, treatment outcomes will improve and cancer diagnoses and related deaths in family members will be prevented.”
The probability of a patient undergoing genetic testing increased over the course of the study, although male breast was the only indication that had a more than 50% likelihood of being tested at any time. The changes over time suggest guidelines may have some effect, with the probability of a pancreatic cancer patient being tested increasing after the release of new recommendations in 2018.
However, the data also suggest that it could be years before most pancreatic cancer patients are tested. The ovarian cancer guidelines have recommended universal genetic testing since 2010, but the probability of being tested stayed below 50% throughout the analyzed period, despite steady gains from 2013 to 2019.
The researchers also identified disparities between the testing rates in racial and ethnic groups. Testing was most common in non-Hispanic white patients, with the rate across male breast, female breast, and ovarian cancer being 31% compared to 22% to 25% in Asian, Black, and Hispanic patients.
The study was released to coincide with a presentation at the 2023 ASCO Annual Meeting in Chicago.
