Low-molecular-weight heparin beyond 12 months in patients with cancer-associated thrombosis.

Background: Clinical guidelines indicate that in patients with cancer-associated thrombosis (CAT), anticoagulant treatment should be continued beyond 6 months as long as the cancer is active. We aimed to analyse the safety of low-molecular-weight heparin (LMWH) beyond 12 months in patients with CAT.

Methods: We performed a post hoc analysis of consecutive CAT patients from October 2008 to December 2019. The primary outcome was the rate of clinically relevant bleeding (CRB), and we compared two periods (1-12 vs. 12-24 months). Hazard ratio (HR), competing risk analysis and sensitivity analyses were performed.

Results: Of the 588 patients included, 30.1% (n = 177) received LMWH beyond 12 months. The rate of CRB in the first 12 months compared to the 12-24 month period was 3.2 per 100 patients/month (95% CI 2.5-4.1) vs. 0.9 per 100 patients/month (95% CI 0.4-1.5), (P < 0.0001). The competing risk analysis of CRB comparing both periods showed a lower sub-distribution hazard ratio (SHR) during the period 12-24 months (SHR: 0.5, 95% CI: 0.3-0.8, P < 0.001).

Conclusion: In patients with cancer-associated thrombosis under anticoagulant treatment with LMWH, the rate of clinically relevant bleeding and major bleeding were lower beyond 12 months.