Bladder cancer in renal allograft recipients: risk factors and outcomes.

Background: Solid organ transplant recipients have an increased cancer risk owing to immunosuppression and oncogenic viral infections. We report on the incidence and types of bladder cancer in kidney transplant recipients in Ireland, describing possible additional risk factors and outcomes in these patients.
Methods: We identified kidney transplant recipients diagnosed with de novo bladder cancer between January 1, 1994, and July 31, 2012, by integrating data from the Irish National Cancer Registry and National Renal Transplant Registry. We calculated the standardized incidence ratio (SIR) and examined patient and tumor characteristics and 1-year survival rate.
Results: Fifteen patients were diagnosed with de novo bladder cancer during the study period, representing 0.48% of kidney transplant recipients. The SIR was 2.5 (95% CI, 1.4-4.2; P < .001). The mean interval between transplantation and diagnosis of bladder tumor was 8.6 years and mean age at time of diagnosis was 55.7 years. Sixty percent of patients were male. The tumor types were transitional cell carcinoma (9 patients), squamous cell carcinoma (3 patients), adenocarcinoma (1 patient), carcinoma in situ (1 patient), and diffuse large B-cell lymphoma (1 patient). Beside immunosuppression, risk factors associated with bladder cancer were urogenital disease (6 patients), cyclophosphamide exposure (2 patients), BK nephropathy (1 patient), analgesic nephropathy (1 patient), and extensive smoking (1 patient). Eight patients underwent radical cystectomy for invasive tumors, with resection of other pelvic organs in 7 patients. Mortality rate within the first year was 40%.
Conclusion: Bladder cancer occurred more commonly in kidney transplant recipients with a predominance of aggressive tumors and a high mortality. In patients with preexisting risk factors such as urologic abnormalities and cyclophosphamide exposure careful assessment before transplantation and vigilant monitoring posttransplantation with a low threshold for cystoscopy may improve outcomes.
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