Abstract P043: A precision medicine gap: limited recognition of colorectal patients eligible for germline testing in molecular residual disease testing setting

Background: Germline testing for hereditary colorectal cancer (CRC) has traditionally been offered to patients with strong cancer family histories, whose colon tumors revealed mismatch repair deficiency (dMMR), and/or individuals diagnosed with CRC under age 50. Underdiagnosis of hereditary cancer syndromes is often attributed to the complexity or unawareness of family history or phenotypic criteria.1,2 The National Comprehensive Cancer Network (NCCN) guidelines for CRC were recently updated (v. 1.2022) to consider germline multigene panel testing (MGPT) evaluation for all individuals with CRC.3,4 Our goal was to evaluate documentation of MGPT in CRC patients referred for molecular residual disease (MRD) testing. Methods: This retrospective cohort study reviewed clinical data submitted to a commercial laboratory for consecutive CRC patients referred from non-academic medical facilities for MRD testing during a two-month study period. Medical diagnoses, treatment history, family history and germline genetic evaluation status were obtained from the test requisition form and pathology reports. Clinical notes were reviewed in 77/80 cases. Results: Of the 80 patients who met criteria for inclusion, 65/80 (81%) had documented MMR testing of their colorectal tumor. Whereas five had abnormal immunohistochemistry, only two (40%) had documented germline results. 19/80 (24%) met NCCN criteria solely based on a personal CRC diagnosis