Venous Thromboembolism and Peri-Operative Chemotherapy for Muscle-Invasive Bladder Cancer: A Population-based Study.

Background: Chemotherapy and major pelvic surgery are established risk factors for venous thromboembolism (VTE). We evaluate the incidence rate, timing, and factors associated with VTE in patients with bladder cancer who underwent radical cystectomy and peri-operative chemotherapy in routine clinical practice.

Methods: Electronic records of treatment were linked to the population-based Ontario Cancer Registry to identify all patients who underwent cystectomy for bladder cancer in Ontario 1994-2013. VTE events within 6 months of before or after cystectomy were identified using diagnostic codes recorded on hospital admissions and emergency department visits. Multivariable logistic regression was used to analyze factors associated with VTE prior to surgery, within 90-days of cystectomy, and 120-days after the start of adjuvant chemotherapy.

Results: 4205 patients had cystectomy and 26% (1084/4205) received peri-operative chemotherapy. The overall incidence rate of VTE within 6 months of cystectomy was 9% (363/4205). VTE rate was highest among those patients treated with neoadjuvant chemotherapy (NACT) compared to patients treated with no chemotherapy or only adjuvant chemotherapy (ACT) (12% vs 8% vs 9%, p  = 0.002). Among all VTE events, 10%, 28%, and 61% occurred before, during, and after hospitalization for cystectomy. Pre-operative VTE rate was highest among cases treated with NACT (4%) compared to patients with no chemotherapy (<1%) or ACT (<1%) ( p  < 0.001). VTE within 90 days of surgery was associated with greater length of hospital admission ( p  < 0.001) across all treatment groups.

Conclusions: A substantial proportion of patients treated with peri-operative chemotherapy will develop VTE. The majority of these occur after discharge from hospital following cystectomy. Extended thromboprophylaxis treatment in high-risk patients including those who receive peri-operative chemotherapy should be considered.