Objectives: To assess the risk of venous thromboembolic events (VTEs) and bleeding with or without thromboprophylaxis during neoadjuvant chemotherapy in bladder cancer patients scheduled for radical cystectomy. Materials and Methods: We conducted a retrospective cohort study in 4886 patients with non-metastatic bladder cancer undergoing cystectomy across 28 centres in 13 countries between 1990 and 2021. Inverse probability weighting analyses were performed to estimate the effect of thromboprophylaxis on VTE and bleeding. Results: In 147 patients (3%) VTEs were recorded within the first year. These occurred a median (interquartile range [IQR]) of 127 (82–198) days after bladder cancer diagnosis. Bleeding events occurred in 131 patients (3%) within the first year. These occurred a median (IQR) of 101 (83–171) days after cancer diagnosis. In inverse probability weighting analyses, compared to patients without thromboprophylaxis during chemotherapy, patients with thromboprophylaxis had not only a lower risk of VTE (hazard ratio [HR] 0.32, 95% confidence interval [CI] 0.12–0.81; P = 0.016) but also a lower bleeding risk (HR 0.03, 95% CI 0.09–0.12; P <0.0001). The retrospective nature of the study was its main limitation. Conclusions: In this retrospective analysis, the benefit of thromboprophylaxis during neoadjuvant chemotherapy before cystectomy is in line with data from randomised trials in other malignancies. Our data suggest thromboprophylaxis is protective against VTEs and should be the standard of care during neoadjuvant chemotherapy.
