Association of Obesity With Mortality and Bleeding in Cancer-Associated Venous Thromboembolism

To assess the prognostic significance of obesity in patients with cancer-associated venous thromboembolism (VTE).

This cohort study used data from the Registro Informatizado de Enfermedad TromboEmbólica (RIETE) registry (2001-2025), a prospective, multicenter registry including patients with objectively confirmed acute VTE. Adults with active cancer and VTE were included if they had normal weight (body mass index 18.5-24.9 kg/m²) or obesity (body mass index ≥30.0 kg/m²). Primary outcome was 90-day all-cause mortality. Secondary outcomes included 1-year all-cause mortality, pulmonary embolism-related mortality, VTE recurrence, and major bleeding. Multivariable logistic regression (for 90-day outcomes), adjusted hazard models (for 1-year outcomes), and time-to-event analyses accounting for competing risks were used.

Among 10,059 patients with cancer-associated VTE, 3748 (37.3%) had obesity. Compared with patients with normal weight, those with obesity were more likely to be female (59.2% vs 45.2%), present with pulmonary embolism (60.5% vs 55.3%), and have hormone-dependent cancers (38.7% vs 23.0%). Obesity was associated with lower 90-day (14.8% vs 26.9%; adjusted odds ratio, 0.68; 95% CI, 0.61 to 0.77) and 1-year all-cause mortality (26.4% vs 42.6%; adjusted hazard ratio, 0.73; 95% CI, 0.67 to 0.79) but higher risk of major bleeding at both time points (90-day adjusted odds ratio, 1.38; 95% CI, 1.11 to 1.73; 1-year adjusted hazard ratio, 1.36; 95% CI, 1.12 to 1.64). VTE recurrence rates were similar between groups.

In this large cohort of patients with cancer-associated VTE, obesity was associated with a lower risk of mortality but a higher risk of major bleeding. These findings support the obesity paradox in this population and highlight the need for personalized approaches to anticoagulation.