Impact of Venous Thrombosis Prevention in Ambulatory Oncology: Importance of Guideline Adherence

PURPOSE: Despite strong evidence and guidelines supporting prophylactic anticoagulation for ambulatory patients with cancer starting systemic cancer-directed therapy who are at high risk of venous thromboembolism (VTE), uptake in practice is limited. We evaluated the real-world impact of prophylactic anticoagulation in such patients receiving guideline-based care. METHODS: We conducted an observational cohort study of patients assessed as part of a multidisciplinary VTE prevention program (the Vermont model) from 2016 to 2021. For this study, we included outpatients at high risk of VTE based on a Khorana risk score or Protecht risk score of ≥3. Based on the individualized decision making, patients either received or did not receive prophylactic anticoagulation. The primary outcome was VTE at 6 months after risk assessment. The secondary outcome was all-cause mortality at 6 months. RESULTS: Of 573 high-risk patients assessed during the study period, 340 (59%) received thromboprophylaxis and 233 (41%) did not. Eleven (3.2%) on thromboprophylaxis developed a VTE within 6 months, compared with 18 (7.7%) not on thromboprophylaxis. After adjusting for age, sex, BMI, cancer stage, chemotherapy, immunotherapy, distance from center, and history of VTE, thromboprophylaxis reduced VTE (adjusted odds ratio [OR], 0.36 [95% CI, 0.16 to 0.80]) compared with no thromboprophylaxis. Of deaths within 6 months, 57 (16.8%) occurred in the thromboprophylaxis group versus 73 (31.3%) in the no thromboprophylaxis group (adjusted OR, 0.46 [95% CI, 0.30 to 0.71]). CONCLUSION: Ambulatory patients with cancer at high risk of VTE who received prophylactic anticoagulation had improved clinical outcomes with fewer VTE events and less mortality. Our real-world data support available clinical trial data and underscore the importance of the provision of guideline-directed care in the cancer outpatient setting.