Risk of Postoperative Venous Thromboembolism after Surgery for Colorectal Malignancy: A Systematic Review and Meta-analysis.

BACKGROUND: Colorectal cancer has the second highest mortality of any malignancy and venous thromboembolism is a major post-operative complication. OBJECTIVE: Determine the variation in incidence of venous thromboembolism following colorectal cancer resection. DATA SOURCES: Following PRISMA and MOOSE guidelines (PROSPERO, ID: CRD42019148828), Medline and Embase databases were searched from database inception to August 2019 including 3 other registered medical databases. STUDY SELECTION: Two blinded reviewers screened studies with a third adjudicating any discordance. Eligibility criteria: Patients post colorectal cancer resection aged ≥18 years old. Exclusion criteria: Patients undergoing completely endoscopic surgery and those without cancer resection. Selected studies were randomized controlled trials and population-based database/registry cohorts. MAIN OUTCOME MEASURES: Thirty- and 90-days incidence rates of venous thromboembolism per 1,000 person-years following colorectal cancer surgery. RESULTS: Of 6,441 studies retrieved 28 met inclusion criteria. 18 were available for meta-analysis reporting on 539,390 patients. Pooled 30 and 90-day incidence rates of VTE following resection were 195 (95% CI 148-256, I2 99.1%) and 91 (95% CI 56-146, I2 99.2%) per 1,000 person-years respectively. When separated by United Nations Geoscheme Areas differences in the incidence of post-operative venous thromboembolism was observed with 30 and 90-days pooled rates per 1,000 person-years of 284 (95% CI 238-339) and 121 (95% CI 82-179) in the Americas and 71 (95% CI 60-84) and 57 (95% CI 47-69) in Europe. LIMITATIONS: High degree of heterogeneity observed within meta-analyses attributable to large cohorts minimizing within study variance. CONCLUSION: The incidence of venous thromboembolism following colorectal cancer resection is high and remains so more than 1-month after surgery. There is clear disparity between the incidence of venous thromboembolism after colorectal cancer surgery by global region. More robust population studies are required to further investigate these geographical differences to determine valid regional incidence rates of venous thromboembolism following colorectal cancer resection.