Lynch Syndrome Screening: A Nationwide Physician Survey Focusing on Factors Influencing Microsatellite Instability Testing Decisions and Early Onset Colorectal Cancer

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Introduction: Prior studies demonstrated that Lynch syndrome (LS) screening by tumor microsatellite instability (MSI) and/or immunohistochemistry (IHC) is not routinely performed in early-onset (< age 50) colorectal cancer (CRC), and CRC generally. As there are no studies assessing factors influencing test ordering decisions and who physicians feel is most responsible for testing, we conducted a national web-based survey. Additionally, we sought to determine variables influencing timing of MSI/IHC result availability as preoperative availability, through colonoscopy biopsy as opposed to surgical resection specimen testing, can assist with decisions on germline genetic testing and extent of colonic resection (ECR).Table: No Caption available.Methods: A 21 question web-based survey was distributed twice to physicians through an American College of Gastroenterology email listing. Results: 4,491 confirmed initial survey receipt. 3,508 confirmed the 2nd. 509 (6.4%) completed the survey with analysis eligibility in 474 (see table 1 with footnote). 97% were gastroenterologists. Table 2 outlines factors preventing MSI/IHC ordering in early-onset CRC. Lack of familiarity interpreting results and cost were most common. Table 3 outlines who is felt to be responsible for ordering MSI/IHC. Only 32.7% felt that gastroenterologists are responsible. In early-onset CRC, 47.2% felt that MSI/IHC should always be performed on colonoscopy, as opposed to surgical resection specimens. Only 30.4% felt if MSI/IHC was ordered on colonoscopy biopsy, surgery should be delayed until results became available. 44.2% were familiar with guidelines for this scenario. Guideline familiarity predicted whether respondents felt surgical resection should be delayed until results returned as this could affect decisions regarding ECR (P=0.0016). Regression analysis demonstrated urban practice location (P=0.026) and GI oncology specialization (P=0.006) were associated with guideline familiarity.Table: No Caption available.Table: No Caption available.Conclusion: Cost and lack of familiarity in interpreting MSI/IHC were the most common factors preventing testing. Importantly, inconsistencies in who is responsible for ordering MSI/IHC may prevent reliable test performance. Lack of guideline familiarity can impede preoperative result availability, thus affecting decisions regarding germline testing and ECR, which may leave patients susceptible to developing a 2nd CRC if not enough colon is removed. Greater attention to guidelines and defined institutional protocols on responsibility and timing of testing are needed.