Details of the study
Germline genetic testing is “increasingly essential for cancer care,” Dr. Kurian said.
It is central to risk-adapted screening and secondary prevention, the use of targeted therapies, including PARP and checkpoint inhibitors, and cascade testing to identify at-risk relatives.
She pointed out that in clinical practice, testing has “evolved rapidly.” Panels include more and more genes. In addition, the cost of these tests is falling, and guidelines have become “more expansive.”
However, “little is known about genetic testing use and results,” Dr. Kurian noted.
The team therefore undertook the SEER-GeneLINK initiative, which involved patients aged ≥ 20 years who were diagnosed with cancer between Jan. 1, 2013, and March 31, 2019, and who were reported to statewide SEER registries in California and Georgia.
The team looked for patients for whom germline genetic test results had been reported by the four laboratories that performed the majority of patient testing in the two states. Results were categorized as pathogenic, benign, or VUS.
The results were classified on the basis of current guidelines for testing and/or management as related to breast/ovarian cancer, gastrointestinal cancer, other hereditary cancers, or those with no guidelines for testing or management.
Dr. Kurian reported that from an overall population of 1,412,388 patients diagnosed with cancer, 1,369,660 were eligible for inclusion. Of those, about half (51.9%) were women, and the majority (86.3%) were aged 50 years or older.
Many of these patients (61.4%) were non-Hispanic White persons, and slightly fewer than half (49.8%) were deemed to be in medium or high poverty, as determined using U.S. Census tract levels.
Overall, germline genetic testing was performed in 93,052 (6.8%) of patients over the study period.
Women were more likely to have undergone germline mutation testing than men, at 13.9% vs. 2.2%, as were patients aged 20-49 years, at 22.1% vs. 8.2% for those aged 50-69 years, and 3.3% for those aged 70 years and older.
The number of genes for which testing was conducted increased from a median of 2 in 2013 to 34 in 2019. Rates of VUS increased more than that for pathologic variants and substantially more so in non-White patients.
By 2019, the ratio of VUS to pathologic variants stood at 1.7 among White patients, vs. 3.9 among Asian patients, 3.6 among Black patients, and 2.2 among Hispanic patients.
The majority of identified pathologic variants that were related to the diagnosed cancer and genes with testing and/or management guidelines accounted for 67.5% to 94.9% of such variants.
Regarding specific cancer diagnoses, Dr. Kurian said that over the course of the study period, testing rates consistently exceeded 50% only among male breast cancer patients.
There were rapid increases in testing for ovarian cancer, from 28.0% of cases in 2013 to 54.0% in 2019. For pancreatic cancer, rates increased from 1.0% to 19.0% over the same period, and for prostate cancer, rates increased from 0.1% to 4.0%. She suggested that these increases in rates may be related to the approval of PARP inhibitors for use in these indications.
However, there was little change in the rates of germline mutation testing for lung cancer patients, from 01% in 2013 to 0.8% in 2019, and for other cancers, from 0.3% to 2.0%.
The results also revealed racial and ethnic differences in testing after controlling for age, cancer type, and year. Over the course of the study period, 8.0% of White patients underwent genetic testing, compared with 6.0% each for Asian, Black, and Hispanic patients and 5.0% for other patients (P < .001).
With regard specifically to male and female breast cancer and ovarian cancer, testing rates were 31% among White patients, 22% for Asian patients, 25% for Black patients, and 23% for Hispanic patients (P < .001).
Dr. Kurian acknowledged that the study is limited by a lack of testing from other laboratories and direct-to-consumer test data, although a recent survey suggested that this represents fewer than 5% of all germline genetic tests.
She also noted that the SEER registries do not collect data on family history or tumor sequencing.
The study was funded by the National Institutes of Health, and the Centers for Disease Control and Prevention. Dr. Kurian has relationships with Adela, Ambry Genetics, Color Genomics, GeneDx/BioReference, Genentech, InVitae, and Myriad Genetics. Other authors report numerous relationships with industry. Dr. Cobain has ties with AstraZeneca, Daiichi Sankyo, Athenex, Ayala Pharmaceuticals, bioTheranostics, and Immunomedics. Dr. Schrag has relationships with Merck, JAMA, AACR, and Grail. Dr. Stadler has ties with Adverum Biotechnologies, Genentech, Neurogene, Novartis, Optos Plc, Outlook Therapeutics, and Regeneron Pharmaceuticals.
A version of this article first appeared on Medscape.com.