Late Anastomotic Leakage After Rectal Cancer Surgery: Incidence and Differential Risk Factors

BACKGROUND: Anastomotic leakage is a major complication of rectal cancer surgery, contributing to increased morbidity, poorer oncologic outcomes, and permanent stoma formation. However, consensus on its diagnostic timeframe and risk factors is lacking. Anastomotic leakage in the late postoperative period is usually under-recognized owing to inconsistent definitions and variable surveillance protocols. OBJECTIVE: To investigate the serial incidence and risk factors for overall and late anastomotic leakage following curative-intent rectal cancer surgery. DESIGN: Retrospective cohort study. SETTINGS: Asan Medical Center, a tertiary referral center in Seoul, Korea. PATIENTS: This study included 4,472 patients who underwent rectal cancer resection with anastomosis between 2012 and 2020. Patients undergoing palliative or combined surgeries were excluded. MAIN OUTCOME MEASURES: We analyzed the incidence and timing of anastomotic leakage and identified independent risk factors for overall and late anastomotic leakage using logistic regression. RESULTS: The overall anastomotic leakage incidence was 3.2% (n = 145), with late anastomotic leakage comprising 48.3% (n=70) of cases. Notably, 24.1% (n=35) were diagnosed over 1 year postoperatively. Of those with late anastomotic leakage, 78.6% (n = 56) had undergone diverting stoma formation. Independent risk factors for overall anastomotic leakage included younger age, male sex, low tumor location, and high inferior mesenteric artery ligation. Late anastomotic leakage was independently associated with neoadjuvant chemoradiotherapy (odds ratio 3.573), robotic surgery (odds ratio 4.734), and adjuvant chemotherapy (odds ratio 3.420). LIMITATIONS: Retrospective design and single-institution surveillance protocol may limit generalizability. CONCLUSIONS: Late anastomotic leakage occurs at a rate comparable to early anastomotic leakage and presents with distinct risk factors. Extended surveillance and tailored management are warranted in high-risk patients. See Video Abstract.