Patients with active cancer are ~5-fold more likely to develop a venous thromboembolism (VTE) than those without. When VTE occurs, cancer patients carry an up to a 3-fold higher rate of thrombosis recurrence and ~twice the risk of bleeding during anticoagulation. Therefore, it is critical to utilize anticoagulants that optimize efficacy while minimizing bleeding risk when treating cancer-associated thrombosis (CAT).

Guidelines list direct-acting oral anticoagulants (DOACs) as an alternative to low molecular-weight heparin (LMWH) for treatment of CAT. The strength-of-recommendation for DOACs is based on data from multiple randomized controlled trials (RCTs) comparing them to LMWHs to treat CAT, with results suggesting DOACs may reduce thrombosis risk but with potentially more frequent bleeding (particularly in those with certain gastrointestinal and genitourinary cancers).

Observational studies evaluating DOACs for CAT treatment have been published, but these studies have been either single-arm, evaluated cancer subtypes not recommended for DOAC treatment, were of limited sample size and/or employed heterogeneous definitions of active cancer. We seek to evaluate the effectiveness and safety of rivaroxaban versus LMWH for CAT treatment in active cancer patients using a large de-identified electronic health record database.

Retrospective cohort analysis using US Optum® De-Identified EHR data. We will use Optum EHR (electronic health records) data from November January 1, 2012 through latest available data (currently September 2020).

Inclusion Criteria:

• Be ≥18 years of age at the time of anticoagulation initiation.
• Have active cancer admitted to the hospital, emergency department or observation unit for acute DVT and/or PE.
• Treated with rivaroxaban (or any DOAC in secondary analysis) or LMWH as their first anticoagulant on day 7 post-acute CAT event diagnosis (index date) o increase the probability of accurately classifying patients' intended outpatient anticoagulant for CAT treatment and that patients are compared at the same point from diagnosis.
• Have been active in the data set for at least 12-months prior to the index event (based on the "First Month Active" field) and had at least one provider visit in the 12-months prior to the acute VTE event (baseline period).

Exclusion Criteria:

• Evidence of atrial fibrillation, recent hip/knee replacement (within 35 days of index VTE), ongoing VTE treatment, valvular heart disease defined as any rheumatic heart disease, mitral stenosis, or mitral valve repair/replacement.
• Pregnancy.
• Initiation of rivaroxaban at a dose other than 15 mg twice daily or non-therapeutic doses of other DOAC or LMWH (e.g., enoxaparin at a dose other than 1 mg/kg twice daily or 1.5 mg/kg once daily; dalteparin at a dose other than 200 IU/kg of total body weight)
• Evidence of use of anticoagulation use during the 12-months prior per written prescription or patient self-report

The Optum EHR database includes longitudinal patient-level medical record data for ~91+ million patients seen at ~700+ hospitals and ~7,000+ clinics across the US. The study population of interest will be patients with cancer, admitted to the hospital, emergency department or observation unit for acute DVT and/or PE on or after January 1, 2013 (to correspond with the US availability of rivaroxaban for VTE treatment), being treated with rivaroxaban (or any DOAC in secondary analysis) or LMWH on day 7 post-acute VTE diagnosis (index date), and have been active in the data set for at least 12-months prior to the index event (based on the "First Month Active" field) and had at least one provider visit in the 12-months prior to the acute VTE event (baseline period).

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