Efficacy of primary prevention of venous thromboembolism among subgroups of cancer patients undergoing chemotherapy: A post-hoc analysis of the AVERT trial

Background: Apixaban has been shown to significantly decrease the rate of VTE among intermediate-to-high risk patients starting chemotherapy compared to placebo. This investigation sought to determine the impact of apixaban among different subgroups of patients with cancer. Methods: This is a pre-planned post-hoc analysis of the AVERT randomized controlled trial which compared apixaban to placebo for the primary prevention of VTE in ambulatory patients initiating chemotherapy. Subgroup analyses were performed based on different baseline characteristics. The primary efficacy outcome was objectively documented major VTE. Hazard ratios (HR) with 95% confidence intervals (CI) were calculated using the Cox proportional hazards model to compare the treatment effect accounting for clustering at study center level. Results: During the study period, major VTE events occurred in 4.2% and 10.2% of the apixaban and placebo groups, respectively (HR 0.41; 95%CI, 0.26-0.65). Characteristics associated with decreased risk of major VTE among patients on apixaban included: male sex (HR 0.25, 95%CI 0.12-0.48); weight > 90Kg (HR 0.18, 95%CI, 0.06-0.52); no prior history of VTE (HR 0.41, 95%CI 0.26-0.64); solid cancers (HR 0.30; 95%CI, 0.19-0.47); metastatic disease (HR 0.45; 95%CI, 0.26-0.78); and concurrent use of antiplatelet therapy (HR 0.18, 95%CI 0.10-0.33). Conclusions: In the AVERT trial, while apixaban thromboprophylaxis reduced the risk of major VTE in most patients, patients with weight > 90 kg, solid cancers, or concurrent antiplatelet therapy experienced the greatest benefits.