Racial and Ethnic Disparities in Germline Genetic Testing of Patients With Young-Onset Colorectal Cancer

Background & Aims: Up to 20% of younger patients (age <50 years) diagnosed with colorectal cancer (CRC) have germline mutations in cancer susceptibility genes. Germline genetic testing may guide clinical management and facilitate earlier intervention in affected relatives. Few studies have characterized differences in genetic testing by race/ethnicity. Methods: We identified young adults (age 18-49 years) diagnosed with CRC between 2009 and 2017 in 2 health systems in Dallas, TX. We evaluated referral to genetic counseling, attendance at genetic counseling appointments, and receipt of germline genetic testing by race/ethnicity. Results: Of 385 patients with young-onset CRC (median age at diagnosis 44.4 years), 176 (45.7%) were Hispanic, 98 (25.4%) non-Hispanic Black, and 111 (28.8%) non-Hispanic White. Most patients (76.9%) received immunohistochemistry (IHC) for mismatch repair proteins, and there was no difference in receipt of IHC by race/ethnicity. However, a lower proportion of Black patients were referred to genetic counseling (50.0% vs White patients 54.1% vs Hispanic patients 65.9%; P = .02) and attended genetic counseling appointments (61.2% vs 81.7% White patients vs 86.2% Hispanic patients; P < .01). Of 141 patients receiving genetic testing, 38 (27.0%) had a pathogenic or likely pathogenic variant in a cancer susceptibility gene. An additional 33 patients (23.4%) had variants of uncertain significance, of which 84.8% occurred in racial/ethnic minorities. Conclusions: In a diverse population of patients diagnosed with young-onset CRC, we observed racial/ethnic differences in referral to and receipt of germline genetic testing. Our findings underscore the importance of universal genetic testing to address racial/ethnic disparities in young-onset CRC.