Venous thromboembolism and effect of comorbidity in bladder cancer: A danish nationwide cohort study of 13,809 patients diagnosed between 1995 and 2011.

OBJECTIVES

Bladder cancer (BC) is associated with venous thromboembolism (VTE), but data on the effect of comorbidities are scarce.

MATERIALS AND METHODS

Population-based cohort study with 13,809 patients with BC diagnosed in Denmark (1995-2011) and a general population comparison cohort matched on age, sex, and comorbidities (n = 132,421). Risk of VTE, pulmonary embolism and deep venous thrombosis was computed for the first month, 3 months, 1 year, and 5 years following cancer diagnosis and stratified by Charlson Comorbidity Index (CCI) scores, cystectomy, and metastases.

RESULTS

VTE risk was higher among the patients with BC than in the comparison cohort during five years of follow-up (risk difference = 20 per 1,000 persons [95% CI: 16-23]). Excess risk was relatively stable with increasing comorbidity score. In the first year, the risk difference was 17 per 1,000 persons (95% CI: 14-21) and 16 (95% CI: 4.8-27) for CCI score = 0 and CCI score = 4, respectively, and similar results were observed by stratification on pulmonary embolism and deep venous thrombosis. For patients with BC undergoing cystectomy, VTE risk was 70-fold higher than in the general population cohort within 3 months after diagnosis.

CONCLUSIONS

BC is associated with increased risk of VTE, compared with the general Danish population. Risks are particularly high for VTE after cystectomy. Risk did not increase with higher comorbidity burden, as the relative risk of VTE was greatest among patients without comorbidity. Clinical attention to VTE risk, particularly cystectomy-related VTE, in patients with BC is appropriate irrespective of comorbidities.