Germline Genetic Testing After Cancer Diagnosis

Abstract

ImportanceGermline genetic testing is recommended by practice guidelines for patients diagnosed with cancer to enable genetically targeted treatment and identify relatives who may benefit from personalized cancer screening and prevention.ObjectiveTo describe the prevalence of germline genetic testing among patients diagnosed with cancer in California and Georgia between 2013 and 2019.Design, Setting, and ParticipantsObservational study including patients aged 20 years or older who had been diagnosed with any type of cancer between January 1, 2013, and March 31, 2019, that was reported to statewide Surveillance, Epidemiology, and End Results registries in California and Georgia. These patients were linked to genetic testing results from 4 laboratories that performed most germline testing for California and Georgia.Main Outcomes and MeasuresThe primary outcome was germline genetic testing within 2 years of a cancer diagnosis. Testing trends were analyzed with logistic regression modeling. The results of sequencing each gene, including variants associated with increased cancer risk (pathogenic results) and variants whose cancer risk association was unknown (uncertain results), were evaluated. The genes were categorized according to their primary cancer association, including breast or ovarian, gastrointestinal, and other, and whether practice guidelines recommended germline testing.ResultsAmong 1 369 602 patients diagnosed with cancer between 2013 and 2019 in California and Georgia, 93 052 (6.8%) underwent germline testing through March 31, 2021. The proportion of patients tested varied by cancer type: male breast (50%), ovarian (38.6%), female breast (26%), multiple (7.5%), endometrial (6.4%), pancreatic (5.6%), colorectal (5.6%), prostate (1.1%), and lung (0.3%). In a logistic regression model, compared with the 31% (95% CI, 30%-31%) of non-Hispanic White patients with male breast cancer, female breast cancer, or ovarian cancer who underwent testing, patients of other races and ethnicities underwent testing less often: 22% (95% CI, 21%-22%) of Asian patients, 25% (95% CI, 24%-25%) of Black patients, and 23% (95% CI, 23%-23%) of Hispanic patients (P < .001 using the χ2 test). Of all pathogenic results, 67.5% to 94.9% of variants were identified in genes for which practice guidelines recommend testing and 68.3% to 83.8% of variants were identified in genes associated with the diagnosed cancer type.Conclusions and RelevanceAmong patients diagnosed with cancer in California and Georgia between 2013 and 2019, only 6.8% underwent germline genetic testing. Compared with non-Hispanic White patients, rates of testing were lower among Asian, Black, and Hispanic patients.

Genetic Testing for Cancer Susceptibility

“…The analyses by Kurian et al did not identify reasons for underuse of genetic testing. Potential explanations can be divided into at least 2 categories.…”

“…In this issue of JAMA , Kurian et al report the rate of genetic testing in inherited cancer susceptibility in more than 1.36 million patients diagnosed with cancer between 2013 and 2019. Kurian et al linked genetic test results from the 4 major commercial laboratories to incident cancer diagnoses reported to the California and Georgia Surveillance, Epidemiology, and End Results tumor registries. Kurian et al report that only 6.8% of patients with cancer underwent genetic susceptibility testing within 2 years of the cancer diagnosis.…”

“…Kurian et al linked genetic test results from the 4 major commercial laboratories to incident cancer diagnoses reported to the California and Georgia Surveillance, Epidemiology, and End Results tumor registries. Kurian et al report that only 6.8% of patients with cancer underwent genetic susceptibility testing within 2 years of the cancer diagnosis. The testing rates were higher for male breast cancer and ovarian cancer, for which practice guidelines recommend universal testing for all diagnosed patients.…”

“…Some cancer patients may have obtained genetic testing through direct-to-consumer laboratories and would not have been counted among the patients with genetic testing in the analyses. Nonetheless, the low rates of cancer genetic testing reported by Kurian et al raise concern and should stimulate interventions to increase rates of genetic testing with the goal of reducing cancer burden.…”

“…A strength of the study by Kurian et al was measurement of testing at the population level using the California and Georgia statewide tumor registries. When the results were analyzed by race and ethnicity, 22% of Asian patients, 25% of Black patients, and 23% of Hispanic patients underwent genetic testing for male breast cancer, female breast cancer, or ovarian cancer compared with 31% of non-Hispanic White patients with these cancer types.…”