Impact of antiphospholipid antibodies on thrombotic events in ambulatory cancer patients.

Background: Despite the conflicting data, the positivity of antiphospholipid antibodies (aPL) in cancer patients may be associated with an increased risk of thrombosis.

Objective: To identify the prevalence and impact of aPL on venous thromboembolic events (VTE) and arterial thrombosis (ATE) in ambulatory cancer patients.

Methods: In this single-center, prospective cohort study, we enrolled newly diagnosed ambulatory cancer patients receiving chemotherapy. Non-cancer controls were age- and sex-matched. Participants were evaluated for aPL. Primary outcomes were the composite outcome of VTE or ATE and the prevalence of aPL positivity in cancer patients. Secondary outcomes included the risk of VTE and ATE in cancer patients and all-cause mortality at six-month follow-up duration.

Results: There were 137 cases and 137 controls with mean age of 56.0±12.3 and 55.5±12.1 years, respectively. Cancer patients were more likely to have positive aPL compared to controls, with the risk difference of 9.4% (95%CI 1.5 to 17.5). Composite of ATE or VTE occurred in 9 (6.6%) in cancer patients and 2 (1.5%) in controls. Cancer patients with aPL positivity were associated with higher risk of ATE or VTE (risk ratio [RR] 3.6, 95% CI 1.04-12.4). Positive LA in cancer patients were associated with higher risk of composites of ATE or VTE (RR 5.3 95%CI 1.3-21.0), whereas the anti-β2-GPI positivity were associated with increased risk of VTE (RR 4.7, 95%CI 1.1-19.2).

Conclusion: aPL was more prevalent in active cancer patients and positive aPL in cancer patients was associated with arterial or venous thrombosis.