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

Abstract

To assess the prognostic significance of obesity in patients with cancer-associated venous thromboembolism (VTE). This cohort study used data from the 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 (BMI 18.5-24.9 kg/m²) or obesity (BMI ≥30.0 kg/m²). Primary outcome was 90-day all-cause mortality. Secondary outcomes included 1-year all-cause mortality, pulmonary embolism (PE)-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, 3,748 (37.3%) had obesity. Compared with patients with normal weight, those with obesity were more likely to be female (59% vs. 45%), present with PE (60% vs. 55%), and have hormone-dependent cancers (39% vs. 23%). Obesity was associated with lower 90-day (15% vs. 27%; adjusted odds ratio [aOR]: 0.69; 95%CI: 0.61-0.77) and 1-year all-cause mortality (26% vs. 43%; adjusted hazard ratio [aHR]: 0.73; 95%CI: 0.67-0.79), but higher risk of major bleeding at both time points (90-day aOR: 1.38; 95% CI: 1.11-1.73; 1-year aHR: 1.36; 95% CI: 1.12-1.64). 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.