QS207 - Rectifying Referrals: Genetics Is Being Underutilized In Rectal Cancer

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Purpose/Background: The National Comprehensive Cancer Network recommends that all colon and rectal cancer be tested for microsatellite instability (MSI) and/or mismatch repair (MMR), as positive findings could be used to trigger a referral to genetics for workup of Lynch Syndrome and other hereditary colorectal cancer syndromes. There have been studies showing poor adherence with guidelines for genetic counseling referrals. Patient compliance with these referrals has also been shown to be less than ideal in many cases. There are some interventions, such as offering telehealth genetics counselling and standardizing intake forms to collect history pertinent to Lynch Syndrome clinical criteria, that could improve appropriate referral rates and patient compliance. There is little data on genetic testing efficacy for rectal cancer alone, as colon and rectal cancer are frequently treated as one entity, despite clear molecular, epidemiologic, and biologic differences between the two. The purpose of this study was to characterize our institution’s experience with evaluating rectal cancer patients for Lynch Syndrome and other germline mutations, as well as to identify factors that could contribute to facility and patient adherence with genetic referral and testing guidelines.

Methods/Interventions: A retrospective review was conducted for patients diagnosed with rectal cancer at a single site tertiary care hospital from the years 2018, 2019, and 2023. Years 2020-2022 were excluded to avoid confounding factors associated with the COVID-19 pandemic. Demographic, pathology, personal and familial history, treatment, and referral data were collected by chart review. Indications for genetic testing and referral were determined according to recent guidelines published by the Collaborative Group of the Americas on Inherited Colorectal Cancer. Statistical analysis was performed using R version 4.0.3 statistical software.

Results/Outcomes: A total of 141 patients, age ranging from 29 to 96 years, met criteria, of which 122 (81.9%) had MMR and/or MSI testing performed and 34 (24.1%) had indications for genetics referral. Among the latter, 13 (38.2%) were referred to genetic counseling, and of those, 8 (61.5%) saw a genetic counselor or had genetic testing done. There was no statistically significant association between insurance type and referral rate or compliance.

Among those who underwent genetic testing, 3 were positive for mutations; 1 was found to be heterozygous for an MLH1 mutation and diagnosed with Lynch Syndrome, and the other 2 were diagnosed with MUTYH-associated polyposis.

Conclusion/Discussion: This study demonstrates poor adherence with germline mutation testing recommendations in rectal cancer patients, as well as poor patient compliance with genetic referrals. Although rectal cancer comprises a smaller proportion of index cancers in Lynch Syndrome, a high degree of suspicion should be maintained. Lynch Syndrome and hereditary syndromes as a whole have been reported to account for 2-4% and 6-10% of all colorectal cases, respectively, and in our study, several patients tested positive for germline mutations and benefited from subsequent changes in their disease management.