Multigene Panel Testing Yields High Rates of Clinically Actionable Variants Among Patients With Colorectal Cancer

Whether germline multigene panel testing (MGPT) should be performed in all individuals with colorectal cancer (CRC) remains uncertain. Therefore, we aimed to determine the yield and potential clinical impact of MGPT across a large, diverse CRC cohort. METHODS: This was a retrospective cohort study of adults with CRC who underwent MGPT of > 10 genes at a commercial laboratory between March 2015 and May 2021. All data were prospectively collected through a single commercial laboratory and retrospectively analyzed. RESULTS: A total of 34,244 individuals with a history of CRC underwent germline MPGT and were included in the analysis. This cohort was predominantly female (60.7%), White (70.6%), and age 50 years or older (68.9%), with 35.5% also reporting a noncolorectal malignancy. At least one pathogenic/likely pathogenic germline variant (PGV) was found in 4,864 (14.2%), with 3,111 (9.1%) having a PGV associated with increased CRC/polyposis risk and 1,048 (3.1%) having an otherwise clinically actionable PGV. Larger gene panels were not clearly associated with higher yield of clinically actionable PGVs. PGVs were more prevalent in individuals of Ashkenazi Jewish descent (P < .001) and Hispanic ethnicity (P < .001). Across all ages, panel sizes, and races/ethnicities, the rate of clinically actionable PGVs on MGPT was 7.9% or greater. A variant of uncertain significance was identified in 13,094 individuals (38.2%). Identification of a variant of uncertain significance associated with panel size (P < .001) and was lower in individuals of Ashkenazi Jewish descent (P < .001), but higher in Black, Asian, and Hispanic individuals (P < .001). CONCLUSION: To our knowledge, this is the largest study to date examining MGPT in CRC, demonstrating high rates of clinically actionable variants detected across all age groups, panel sizes, and racial/ethnic groups. This work supports consideration of broadening germline genetic testing criteria for individuals with CRC.