Older soft tissue sarcoma patients experience increased rates of venous thromboembolic events: a retrospective cohort study of SEER-Medicare data

BACKGROUND: Venous thromboembolic co-morbidities can have a significant impact on treatment response, treatment options, quality of life, and ultimately, survival from cancer. There is a dearth of published information on venous thromboembolic co-morbidity among older soft tissue sarcoma patients. METHODS: SEER-Medicare linked data (1993-2005) was utilized for this retrospective cohort analysis (n = 3,480 soft tissue sarcoma patients). Non-cancer patients were frequency-matched by age to cancer patients at a ratio of 1:1; coverage and follow-up requirements were the same as for soft tissue sarcoma cases. Venous thromboembolic events were divided into three groups of interest: deep vein thrombosis, pulmonary embolism, and other thromboembolic events. Relative incidence rates of venous thromboembolic events in soft tissue sarcoma patients with a recent history of cardiovascular event or venous thromboembolic event (12 months before diagnosis) versus soft tissue sarcoma patients without such a recent history were calculated using the Cox proportional hazard models. The Cox proportional hazard model was used to build predictive models to identify important risk factors for each venous thromboembolic event of interest among soft tissue sarcoma patients. Relative incidence rate of VTEs in cancer patients (12 months after diagnosis) versus non-cancer cases (12 months after index date) was calculated using multivariable Cox proportional hazard models. RESULTS: We observed that among older soft tissue sarcoma patients, 10.6% experienced a deep vein thrombosis, 3.0% experienced a pulmonary embolism, and 3.1% experienced other thromboembolic events in the 12 months after sarcoma diagnosis. On average, 60% of venous thromboembolic events occurred in the first 90 days after sarcoma diagnosis. The highest rates of deep vein thrombosis and pulmonary embolism after sarcoma diagnosis were seen in patients with sarcoma not otherwise specified (deep vein thrombosis: 204/1,000 p-y and pulmonary embolism: 50/1,000 p-y). Recent history of a venous thromboembolic event was the strongest predictor of a subsequent venous thromboembolic event after soft tissue sarcoma diagnosis. CONCLUSION: Venous thromboembolic events are common and serious co-morbidities that should be closely monitored in older soft tissue sarcoma patients.