The timing of venous thromboembolism in ovarian cancer patients: A nationwide Danish cohort study

Background and aim Venous thromboembolism (VTE) is associated with excess mortality and morbidity in cancer, and is influenced by patient‐, tumor‐, and treatment‐related factors. We aimed to investigate the impact of such factors in a national cohort of patients with epithelial ovarian cancer (EOC). Methods Patients in the Danish Gynecologic Cancer Database (DGCD) with EOC from 2005 to 2014 were followed from time of diagnosis to VTE, or censoring. Surgery, chemotherapy, and vascular epithelial growth factor (VEGF)‐inhibitors were included as time‐varying exposures in Cox proportional hazard regression models. Results A total of 551 VTE events were registered in 4991 EOC patients. Median follow‐up time was 2.9 years. The 2‐year cumulative incidence of VTE was 7.2%. Patients were at highest risk during the first year after EOC diagnosis. Previous VTE was associated with a hazard ratio (HR) of 3.26 (95% confidence interval [CI] 2.42–4.39). Exposure to major pelvic surgery was associated with a HR of 3.21 (95% CI 2.29–4.50). Exposure to chemotherapy or (VEGF)‐inhibitors were associated with HRs of 1.91 (95% CI 1.56–2.33) and 1.05 (95% CI 0.57–1.93), respectively. Hazard ratios for patients with clear cell histopathology was 1.46 (95% CI 0.97–2.20) and 2.42 for International Federation of Gynaecology and Obstetrics stage III‐‐IV (95% CI 1.93–3.03). Conclusions EOC is associated with a high risk of VTE, particularly within the first year after diagnosis. Major pelvic surgery and chemotherapy were strongly associated with VTE. Person‐related risk factors were increasing age and previous VTE. Advanced stage was an independent tumor‐related risk factor. These findings support the indication for thrombosis prophylaxis during chemotherapy.