Sex difference for urologic malignancy risk in uremic patients after kidney transplantation: a population-based study.

BACKGROUND: High urologic malignancy incidence has been reported in end-stage renal disease (ESRD) patients, especially of female sex. This study was undertaken to evaluate whether female recipients still carry an aggravated risk of this malignancy after kidney transplantation (KT). METHODS: The claims data from the Bureau of National Health Insurance of Taiwan were used for analysis. All KT recipients who developed urologic malignancy from January 1, 1999, to December 31, 2007 (n = 2,245) were enrolled in this study. By means of propensity score, a database of 1:4 ratio random incident ESRD patients with matched age, sex, comorbidity rates, and dialysis to index date was used as control (non-KT group, n = 8,980). The last observation period ended on December 31, 2008. RESULTS: The cumulative urologic malignancy incidence rate was significantly higher in female recipients after KT than their female ESRD counterparts without KT (P < 0.001). This gap became more prominent approximately 2 years after transplantation. No similar trend was detected in male KT patients (P = 0.13). Incidence rate ratio of urologic malignancy was significantly higher in female recipients (incidence rate ratio, 2.13; 95% confidence interval [95% CI], 1.53-2.97) than in their male counterparts (incidence rate ratio, 1.43; 95% CI, 0.90-2.25). From multivariate Cox proportional hazard regression tests, female (hazards ratio, 2.10; 95% CI, 1.52-2.95) but not male sex (hazards ratio, 1.47; 95% CI, 0.93-2.32) was determined to be an independent factor for the development of urologic malignancy after KT. After acquiring this malignancy, KT recipients did not have any advantage in cumulative survival compared to ESRD patients without KT (P = 0.07). CONCLUSION: Compared to males, female recipients tended to have a significantly higher urologic malignancy risk after KT.