Barriers in the identification and diagnosis of hereditary colon cancer.

Abstract

e13524 Background: Lynch Syndrome (LS), the most common form of hereditary colorectal cancer (CRC), is due to germline pathogenic variant (PV) in mismatch repair genes (MMR). Since 2009, the National Comprehensive Cancer Network (NCCN) recommends MMR screening for LS for all CRCs regardless of age. The American College of Medical Genetics and Genomics recommends patients with MMR deficiency or microsatellite instability (MSI) be referred for genetic testing. Despite these recommendations, compliance is low. The aim of this study was to evaluate compliance with LS screening and genetic testing in CRC. Methods: A single institution retrospective review of patients diagnosed with CRC from 2018-2021 was performed. A chart review of those diagnosed in 2018 and 2021 was analyzed and combined as a single population from pre and post COVID periods. A student’s T-Test was used to compare continuous variables and chi square for categorical variables within the two populations. The compliance with either MSI or MMR screening was calculated. Meeting criteria for genetic testing was defined as age less than 50, MSI-L/H or MMR deficient. These patients were then analyzed to determine the proportion of genetic referrals, genetic counseling, genetic testing and identification of LS. Results: 276 patients with CRC were reviewed, 153 in 2018, 123 in 2021. 71.2% were Caucasian and 58% male. There was no statistically significant difference in gender, race or ethnicity, however, there was a difference in age, with a younger average age in 2021 (67, 63; p = 0.014). 146 (53%) patients were screened for LS. 44 (16%) with MSI, 19 (7%) MMR and 82 (30%) with both. 78 patients met criteria for genetic testing; 47 due to age alone, 6 age and positive LS screening and 25 screening alone. 35% (27/78) of those meeting criteria were referred to genetics, of which 63% (17/27) completed their appointment, 63% (17/27) were tested, and 37% (10/27) had a PV identified. Conclusions: Despite guidelines for LS screening, compliance is low with only half of CRC patients appropriately screened at our institution. Even patients with positive screening and those less than 50 were not referred for genetic testing. However, of referred patients, 63% completed their appointment and all those were tested. This supports the idea that poor compliance with genetic testing is not due to patient compliance, but shows a systems issue at a higher level. To improve LS identification, reflex screening and genetic referrals are paramount. In our study, 59% of patients with germline testing had a PV, however 65% of those meeting criteria were never referred, which could reflect a proportion of patients with LS going unidentified. This validates the 2022 NCCN guidelines recommending genetic testing for all CRCs despite age or MSI/MMR status. By removing the barrier of MMR testing, more genetic testing will likely be done. [Table: see text]