Renal cell carcinoma in native kidneys before transplantation - When will we stop waiting?

Introduction: Kidney transplantation requires immunosuppression, traditionally regarded as a risk factor for progression in all malignancies. Based on the Cincinnati Registry, a waiting period before transplantation is therefore mandatory. However, recent evidence suggests this increased risk is restricted to particular tumors, whereas others like renal cell carcinoma (RCC) are not negatively affected. We aimed to compare oncological outcomes of RCC in native kidneys of end-stage renal disease (ESRD) patients, according to their transplantation or dialysis status. Material and methods: Retrospective analysis of all ESRD patients diagnosed with RCC between 2010 and 2020 in our center. Recurrence-free survival (RFS) and overall survival (OS) were estimated with Kaplan-Meier curves. Multivariable Cox regression model was used to evaluate their association with kidney transplantation. Results: Clinical and pathological characteristics were similar between groups. Kidney transplant recipients had similar risk of recurrence (hazard ratio [HR] 0.40, 95% confidence interval [CI) 0.04-4.46, p = 0.458) and overall survival (HR 0.34, 95%CI 0.07-1.77, p = 0.202) as dialyzed patients. On multivariable Cox regression model, presence or absence of transplantation was not significantly associated with RFS (p = 0.479) or OS (p = 0.236). Time on dialysis was the only independent predictor of worse survival (HR 1.86, 95%CI 1.18-2.93, p = 0.008). Conclusions: Most RCC in native kidneys of ESRD patients are low-grade, low-stage and exhibit favourable pathological and outcome features. Immunosuppression does not seem to have an impact on oncological outcomes, but an increased time on dialysis seems to be associated with worse overall survival. Therefore, waiting time for transplantation for these tumors could be reduced.