Venous thromboembolism and secondary outcomes of bleeding and mortality in patients with gliomas: a multicenter cohort study

Introduction Venous thromboembolism (VTE) is a common and clinically significant complication in Central Nervous system (CNS) tumors, associated with increased hospitalization, morbidity, and mortality. This study estimates the cumulative incidence of VTE, bleeding, and all-cause mortality in patients with primary gliomas and evaluates their determinants using multivariable models accounting for competing risks, confounding, and missing data. Methods This multicenter retrospective cohort study evaluated 334 adults with histologically confirmed primary gliomas treated across nine Brazilian centers (2021–2022; follow-up to December 2023). Outcomes included VTE, bleeding, and all-cause mortality. Sociodemographic, clinical, tumor-specific, treatment, and thromboprophylaxis data were collected. Twelve-month cumulative incidence was estimated using competing-risk methods. VTE and bleeding were assessed with Fine–Gray sub distribution hazard models, and mortality with Cox proportional hazards models. Results VTE and bleeding cumulative incidences at 12 months were 11.8% (8.0 – 15.5% CI) and 4.7% (2.1 – 7.3% CI). The cumulative mortality incidence was 26.2%. Prior VTE (SHRadj = 4.28; 95% CI 2.60 – 7.07) and corticosteroid use (SHRadj = 3.25; 95% CI 2.20 – 4.81) independently increased VTE risk. Chronic kidney failure (SHRadj = 6.45; 95% CI 5.39 – 7.73) and diabetes mellitus SHRadj = 2.11; 95% CI: 1.51 – 2.95) were the independent predictor of bleeding. For mortality, gliomas NOS (HRadj = 9.20; 95% CI: 5.38–15.73) and GBM (HRadj = 10.34; 95% CI 4.28 – 24.96) were strongly associated with increased risk. Longer hospitalization (≥7 days; HRadj = 2.01; 95% CI 1.81 – 2.24), postoperative bleeding (HRadj = 2.92; 95% CI 2.10 – 4.13), and treatment in specialized cancer centers (HRadj = 2.59; 95% CI: 1.50 – 4.50), along with demographic characteristics, were also associated with higher mortality. Conclusion In this multicenter Brazilian cohort of patients with primary gliomas, VTE was frequent, while bleeding was less common but clinically relevant. Mortality risk was driven by patient characteristics, tumor aggressiveness, and hospitalization factors, underscoring the need for individualized risk stratification. Within the subgroup analysis for mortality, higher educational level was associated with lower hazard of death, whereas prolonged hospitalization and postoperative bleeding consistently increased mortality risk across both GBM and grade 3 or 4 tumors.