Incidence, Timing, and Outcomes of Venous Thromboembolism in Patients Undergoing Surgery for Esophagogastric Cancer: A Population-Based Cohort Study

Background Abdominal surgery and chemotherapy are well-established risk factors for venous thromboembolism (VTE) in patients with cancer, but their specific contribution in patients with esophageal and gastric cancer is unclear. We aim to quantify the risk of VTE, identify risk factors associated with VTE, and determine the association between VTE and survival in patients undergoing surgery for esophageal or gastric cancer. Methods A retrospective, population-based cohort study was conducted using linked administrative healthcare databases. We used the Ontario Cancer Registry to identify patients with esophageal or gastric cancer between January 1, 2007 and December 31, 2016 who underwent surgical resection. Incidence of first VTE event was identified using International Classification of Diseases 9 and 10 codes. VTE incidence was calculated at clinically relevant time points 180 days before and after surgery. Logistic regression was used to identify factors associated with VTE with odds ratios (OR) and 95% confidence intervals (CI) reported. Cox proportional hazards regression models were used to estimate associations between covariates and survival. Kaplan-Meier method was used to compare overall (OS) and cancer-specific survival (CSS) by VTE status. Results A total of 4894 patients had esophagectomy or gastrectomy, of which 8% (n = 383/4894) had VTE. VTE risk was 2.5% (n = 123/4894) 180 days before surgery, 2.8% (n = 138/4894) within 30 days of surgery, and 2.5% (n = 122/4894) from 31 to <= 180 days after surgery. Of the patients with VTE within 30 days of surgery, 34% (n = 47/138) were diagnosed after discharge from hospital. Receipt of preoperative chemotherapy was associated with VTE 180 days before surgery (odds ratio [OR] 3.84, 95% confidence interval [CI] 2.41, 6.11). Increased hospital length of stay (LOS) was associated with VTE 30 days after surgery (OR 1.08, 95% CI 1.02, 1.14, per week). Patients with VTE had inferior median OS and CSS (2.2 vs. 3.7 years; 2.3 vs. 4.4 years, respectively). In adjusted models VTE was associated with inferior OS (HR 1.36, 95% CI 1.13, 1.63) and CSS (HR 1.42, 95% CI 1.16, 1.75). Conclusions The highest risk of VTE is within 30 days of surgery with one third of patients diagnosed after discharge from hospital. Longer hospital LOS and receipt of preoperative chemotherapy are associated with increased risk of VTE. VTE is an independent risk factor for inferior survival in patients with esophageal or gastric cancer.