To compare the efficacy and safety of antithrombotic prophylaxis given for 1 week or 4 weeks in patients undergoing laparoscopic surgery for colorectal cancer.

Extending antithrombotic prophylaxis beyond 1 week reduces the incidence of venous thromboembolism (VTE) after open abdominal surgery for cancer.

In consecutive patients who underwent laparoscopic surgery for colorectal cancer, complete compression ultrasonography of the lower limbs was performed after 8 ± 2 days of antithrombotic prophylaxis. Patients with no evidence of VTE were randomized to short (heparin withdrawal) or to extended (heparin continued for 3 additional weeks) prophylaxis. Complete compression ultrasonography was repeated at day 28 ± 2 after surgery by investigators blinded to treatment allocation. The primary outcome of the study was the composite of symptomatic and ultrasonography-detected VTE at day 28 ± 2 after surgery.

Overall, 301 patients were evaluated for inclusion in the study and 225 were randomized. VTE occurred in 11 of 113 patients randomized to short (9.7%) and in none of the 112 patients randomized to extended heparin prophylaxis (P = 0.001). The incidence of VTE at 3 months was 9.7% and 0.9% in patients randomized to short or to extended heparin prophylaxis, respectively (relative risk reduction: 91%, 95% confidence interval: 30%-99%; P = 0.005). The rate of bleeding was similar in the 2 treatment groups. Two patients died during the study period, 1 in each treatment group.

After laparoscopic surgery for colorectal cancer, extended antithrombotic prophylaxis is safe and reduces the risk for VTE as compared with 1-week prophylaxis (NCT01589146).