NEW YORK – Researchers have found that germline genetic testing rates for cancer patients are low in California and Georgia, even though practice guidelines recommend such testing for certain cancer types.
In a new observational study published in JAMA on Monday, researchers at Stanford University and elsewhere found that only 6.8 percent of patients diagnosed with cancer in California and Georgia between 2013 and 2019 underwent germline genetic testing.
"Many cancer patients who should receive genetic testing are not receiving it — and thus are missing out on opportunities for genetically targeted therapies, such as poly (ADP-ribose) polymerase inhibitors, that have been shown to save lives," lead and corresponding author Allison Kurian, a professor of medicine and of epidemiology and population health at Stanford University, said in an email.
Germline genetic testing evaluates inherited mutations and can improve survival rates among cancer patients by guiding the use of genetically targeted therapies. Moreover, it helps assess cancer risk in family members of patients, leading to better screening and preventive therapies.
Kurian and colleagues used data from state cancer registries of California and Georgia, which track every cancer diagnosed in their state, and linked them to genetic testing results from the four laboratories that provide most such testing. These included patients aged 20 years or older who had been diagnosed with any type of cancer between January 2013 and March 2019.
Among 1,369,602 patients diagnosed with cancer in the two states during that time, 93,052, or 6.8 percent, underwent germline testing through March 31, 2021, the researchers found. While the numbers increased over time, they didn't hit the mark.
"We found that genetic testing use falls far short of practice guidelines," Kurian said. In particular, only half of all male breast cancer patients, 39 percent of ovarian cancer patients, and 6 percent of pancreatic cancer patients were tested, even though guidelines recommend that all patients with these cancers should receive germline testing.
The study also highlighted racial and ethnic disparities in the rates of testing. Asian, Black, and Hispanic patients were tested less often than non-Hispanic White patients. "This is particularly concerning," Kurian said.
One of the reasons, the authors suggested, could be the high out-of-pocket cost to get the test, which ranges from $100 to $250. "Increased access to both clinical testing and genetics research is needed for underrepresented groups," the authors wrote.
Meanwhile, the researchers found that germline genetic testing rates did not differ by cancer stage, indicating insufficient confirmatory germline testing of patients with advanced cancer who received somatic tumor testing and failure to offer testing to patients’ relatives.
The low rates of germline testing can have dire consequences. "Because clinical trials have demonstrated that germline-directed cancer screening, preventive surgery, and targeted therapies can improve survival, low rates of germline genetic testing may contribute to higher rates of cancer mortality," the authors wrote.
Since data were limited to California and Georgia, the findings may not apply to other states in the US, though, they said.
As next steps, the authors want to study how the results of germline testing inform treatment and how it is associated with patient outcomes, including survival. In addition, the researchers are conducting a randomized clinical trial of approaches to cascade genetic testing of relatives of cancer patients, Kurian said.