Comparative Safety and Effectiveness of Apixaban Versus Rivaroxaban for the Treatment of Venous Thromboembolism: A Systematic Review and Meta-Analysis

Technical Summary: Comparative Safety and Effectiveness of Apixaban Versus Rivaroxaban for VTE Treatment

Problem Statement
Venous Thromboembolism (VTE), encompassing Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE), is a prevalent cardiovascular condition with significant morbidity and mortality. Direct Oral Anticoagulants (DOACs), specifically apixaban and rivaroxaban, are the standard of care for VTE treatment. However, the comparative evidence regarding their safety and effectiveness has remained inconsistent. Previous literature, largely composed of observational studies and indirect comparisons, yielded conflicting conclusions: some suggested rivaroxaban reduced recurrent VTE, others found no significant difference, and some favored apixaban. Furthermore, a recent Randomized Controlled Trial (RCT) by Castellucci (2026) provided new high-quality evidence suggesting apixaban might reduce bleeding and mortality, necessitating a quantitative synthesis of this emerging data alongside existing observational studies to resolve the debate.

Methodology
This study is a systematic review and meta-analysis conducted in accordance with PRISMA guidelines.

• Data Sources: A comprehensive search was performed across PubMed (MEDLINE), Scopus, and the Cochrane Library, supplemented by manual reference checking.
• Eligibility Criteria: The review included Randomized Controlled Trials (RCTs) and non-randomized observational studies (prospective or retrospective cohorts) comparing apixaban to rivaroxaban in patients of any age with VTE. Studies were required to report at least one predefined outcome.
• Included Studies: Nine studies were selected, comprising 8 observational studies and 1 RCT (Castellucci 2026), totaling 95,689 patients.
• Outcomes:
  • Primary: VTE recurrence, all-cause mortality, major bleeding, and clinically relevant non-major bleeding (CRNMB).
  • Secondary: Gastrointestinal (GI) bleeding.
• Statistical Analysis: Data were pooled using a random-effects model in RStudio (meta and metafor packages) with Hazard Ratios (HR) as the effect measure. Heterogeneity was quantified using the $I^2$ statistic and $\tau^2$. Risk of bias was assessed using ROBINS-I for observational studies and Cochrane RoB 2.0 for the RCT. Sensitivity analyses were performed by sequentially removing influential outliers, and subgroup analyses were conducted based on age, cancer status, and follow-up duration.

Key Results
The meta-analysis yielded the following pooled results:

• Major Bleeding: Apixaban was associated with a statistically significant reduction in major bleeding compared to rivaroxaban (HR 0.66, 95% CI 0.50–0.86; $p=0.002$).
• Clinically Relevant Non-Major Bleeding (CRNMB): Apixaban demonstrated a significant reduction in CRNMB (HR 0.59, 95% CI 0.42–0.84; $p=0.003$).
• Gastrointestinal Bleeding: A significant reduction in GI bleeding was observed with apixaban (HR 0.75, 95% CI 0.61–0.92; $p=0.0058$), with no heterogeneity ($I^2=0\%$).
• VTE Recurrence: While apixaban showed a trend toward reduced recurrence (HR 0.76), the result was not statistically significant (95% CI 0.51–1.15; $p=0.19$). High heterogeneity ($I^2=66.8\%$) was noted, which was largely driven by the Dawwas 2018 study; sensitivity analysis removing this outlier shifted the HR to 0.91, further indicating no significant difference.
• All-Cause Mortality: No statistically significant difference was found between the two drugs (HR 0.91, 95% CI 0.75–1.11; $p=0.369$).

Significance and Claims
The authors claim that this meta-analysis provides critical evidence supporting the preferential use of apixaban over rivaroxaban for patients with VTE who are at an increased risk of bleeding. The study concludes that apixaban offers a more favorable bleeding safety profile, evidenced by significant reductions in major, non-major, and gastrointestinal bleeding events.

However, the paper maintains a modest stance regarding efficacy. It asserts that the efficacy of both drugs in preventing VTE recurrence and reducing all-cause mortality appears comparable, with no statistically significant differences observed. The authors highlight that the observed heterogeneity in recurrence and mortality outcomes likely stems from differences in study designs, patient populations, and residual confounding inherent in the predominantly observational dataset (8 out of 9 studies).

The study emphasizes that while apixaban's safety profile is superior, the choice of anticoagulant should be individualized based on patient-specific risk factors, particularly bleeding risk. The authors call for further large-scale, head-to-head randomized studies to reduce confounding and selection bias, and for standardized definitions of bleeding and recurrence to improve future evidence synthesis. They also note the need for dedicated studies on specific subgroups, such as the elderly and cancer patients, where pharmacokinetic differences may alter safety profiles.