Pre-Operative, Intra-Operative, and Post-Operative Factors Associated with Post-Discharge Venous Thromboembolism Following Colorectal Cancer Resection

Background Venous thromboembolism (VTE) is the most common preventable cause of 30-day post-operative mortality, with many events occurring after hospital discharge. High-level evidence supports post-discharge VTE chemoprophylaxis following abdominal/pelvic cancer resection; however, some studies support a more tailored approach. Our objectives were to (1) identify risk factors associated with post-discharge VTE in a large cohort of patients undergoing colorectal cancer resection and (2) develop a post-discharge VTE risk calculator. Methods Patients who underwent colorectal cancer resection from 2012 to 2016 were identified from ACS NSQIP colectomy and proctectomy procedure-targeted modules. Multivariable logistic regression was used to identify factors associated with post-discharge VTE. Incorporating pre-operative, intra-operative, and post-operative variables, a post-discharge VTE risk calculator was constructed and validated. Results Of 51,139 patients, 387 (0.76%) developed post-discharge VTE. Pre-operative factors associated with post-discharge VTE included BMI (e.g., morbidly obese OR 2.27, 95% CI 1.65-3.12 vs. normal BMI), and thrombocytosis (OR 1.41, 95% CI 1.03-1.92). Intra-operative factors included operative time (4-6 h OR 1.56, 95% CI 1.12-2.17; > 6 h, OR 1.85, 95% CI 1.21-2.84, vs. < 2 h), and type of operation (e.g., open partial colectomy OR 1.67, 95% CI 1.30-2.16 vs. laparoscopic partial colectomy). Post-operative factors included anastomotic leak (OR 2.05, 95% CI 1.31-3.21) and post-operative ileus (OR 1.39, 95% CI 1.07-1.79). Using the risk calculator, the predicted probability of post-discharge VTE ranged from 0.04 to 10.29%. On a 10-fold cross validation, the calculator's mean C-Statistic was 0.65. Conclusions Patient-specific factors are associated with varying rates of post-discharge VTE. We present the first post-discharge VTE risk calculator designed for use at the time of discharge following colorectal cancer resection.