eP502 - A Risk-Share Analysis of the Need for Diverting Ileostomies in Rectal Cancer Patients Following Low-Anterior Resection

Purpose/Background: Low anterior resection (LAR), with or without pre-operative chemoradiation, is the mainstay of therapy for rectosigmoid and rectal cancer. One of the most significant complications is an anastomotic leak, affecting anywhere from 3-20% of patients with varying severity. Subsequent risks include sepsis, re-operation, increased short-term mortality, and stoma permanence. A protective ileostomy can reduce the risk of leak to 2.5-6%. However, ileostomies are not without risks or challenges. Very little is known about patient preferences and risk acceptance in the oncologic setting. Our study aims to evaluate patient acceptable thresholds of risk for anastomotic leak before opting for a protective ileostomy via a treatment trade-off method.Methods/Interventions: Participants were recruited from two tertiary care centers within the University Health Network. Eligible patients had rectal cancer, were above 18, and were of any total neoadjuvant therapy, chemoradiation, and surgical status. Patients were excluded if they were unable to understand or read English, or unable to participate in-person or electronically. Standardized patient interviews were conducted where the benefits and risks of an ileostomy were outlined. Patients were informed that the risk of anastomotic leak also meant delayed post-operative recovery and chemotherapy, if indicated. The anatomy and function of an ileostomy were described, including the requirement for a second operation to reverse. The risks shared included dehydration, bowel obstructions, hernia, and stoma permanence. A hypothetical clinical scenario was presented, and patient preferences were elicited. The primary outcome was the threshold at which patients would accept a protective ileostomy due to the risk of anastomotic leak. This was expressed as a median percentage and interquartile range (IQR). Descriptive responses to address rationale were also collected.Results/Outcomes: Among 20 eligible patients, 14 consented and completed the study. Baseline risk for anastomotic leak was set at 5%, with or without a protective ileostomy. The risk of anastomotic leak without an ileostomy was increased by 1% while the risk with an ileostomy remained 5%. The median threshold was 14% (IQR 10-24%) risk of anastomotic leak at which point patients would opt for a protective ileostomy. This reflects an absolute risk increase of 9%. Patients cited their own personal experiences with a stoma as a deciding factor as well as wanting to optimize post-operative recovery. However, only 4 patients (28.6%) had undergone a protective ileostomy and 0 experienced an anastomotic leak after reversal.Conclusion/

Discussion: Patient preferences are an integral part of decision-making in the treatment of colorectal cancer. Offering oncologic resection without an ileostomy is an option for patients despite the increased risk of anastomotic leak to better align with patient values.Table 1Patient Demographics