Cost-Effectiveness of Extended Thromboprophylaxis in Patients Undergoing Colorectal Surgery from a Canadian Health Care System Perspective

Abstract

BACKGROUND: There is increasing evidence to support extended thromboprophylaxis after colorectal surgery to minimize the incidence of postdischarge venous thromboembolic events. However, the absolute number of events is small, and extended thromboprophylaxis requires significant resources from the health care system. OBJECTIVE: This study aimed to determine the cost-effectiveness of extended thromboprophylaxis in patients undergoing colorectal surgery for malignancy or IBD. DESIGN: An individualized patient microsimulation model (1,000,000 patients; 1-month cycle length) comparing extended thromboprophylaxis (28-day course of enoxaparin) to standard management (inpatient administration only) after colorectal surgery was constructed. SETTINGS: The sources for this study were The American College of Surgeons National Surgical Quality Improvement Project Participant User File and literature searches. OUTCOMES: Costs (Canadian dollars), quality-adjusted life-years, and venous thromboembolism-related deaths prevented over a 1-year time horizon starting with hospital discharge were determined. The results were stratified by malignancy or IBD. RESULTS: In patients with malignancy, extended prophylaxis was associated with higher costs (+113$; 95% CI, 102-123), but increased quality-adjusted life-years (+0.05; 95% CI, 0.04-0.06), resulting in an incremental cost-effectiveness ratio of 2473$/quality-adjusted life-year. For IBD, extended prophylaxis also had higher costs (+116$; 95% CI, 109-123), more quality-adjusted life-years (+0.05; 95% CI, 0.04-0.06), and an incremental cost-effectiveness ratio of 2475$/quality-adjusted life-year. Extended prophylaxis prevented 16 (95% CI, 4-27) venous thromboembolism-related deaths per 100,000 patients and 22 (95% CI, 6-38) for malignancy and IBD. There was a 99.7% probability of cost-effectiveness at a willingness-to-pay threshold of 50,000$/quality-adjusted life-year. To account for statistical uncertainty around variables, sensitivity analysis was performed and found that extended prophylaxis is associated with lower overall costs when the incidence of postdischarge venous thromboembolic events reaches 1.8%. LIMITATIONS: Significant differences in health care systems may affect the generalizability of our results. CONCLUSIONS: Despite the rarity of venous thromboembolic events, extended thromboprophylaxis is a cost-effective strategy.