Colorectal organ preservation in Lynch syndrome: A tailored conservative surgical approach.

90 Background: For Lynch syndrome (LS)-associated colorectal cancers(CRC), existing guidelines prefer extended resection for cancer risk reduction. However, life-long compromises in bowel function can result. As patients increasingly value shared decision-making, we evaluated the long-term outcome of a judicious conservative surgical approach allowing colorectal organ-preservation in LS. Methods: LS patients presenting with index (first-in-life) CRC between 2006-2023 were reviewed for clinical and surveillance data. LS was defined by pathogenic germline mutation. Shared decision-making was standard; extended resection was undertaken for patient choice, left-sided colon cancer, synchronous neoplasms. Primary outcome was organ preservation, defined as retaining the majority (>50%) of the colorectum, from index CRC to last contact. Results: Over 17 years, 273 patients presented with 302 index CRCs (233 [77.1%] colon, 69 [22.2%] rectal, with 29 [9.6%] being synchronous). Extended vs. segmental resections were performed in 26 (9.5%) vs. 201(73.6%) patients. The remaining 46 (16.9%) patients had no resection (advanced endoscopic resection in 9, complete clinical response in 21, and asymptotic primary with advanced metastases in 16). The immediate organ preservation rate was 90.5% (89.9% among 257 curative-intent cases). After 1741 person-years of follow-up (mean 6.4+5.5 years), 23 metachronous CRCs underwent repeat surgical (20) or endoscopic (3) resections. The long-term organ preservation rate was 83.2% (82.1% among curative-intent cases). The rate was higher among patients with index rectal cancers. Conclusions: Over 80% of LS patient enjoyed long-term colorectal organ preservation with a judicious conversative surgical approach. It should be strongly considered in the current era of endoscopic advances, immunotherapy, and novel prevention options.