Native kidney small renal masses in patients with kidney transplants: Does chronic immunosuppression affect tumor biology?

Introduction: We compared clinicopathological characteristics and outcomes of radical nephrectomy (RN) for small renal masses (SRM) in patients with end-stage renal disease (ESRD) before or after transplant at a high-volume urologic and transplant center. Methods: We performed a retrospective review of patients with ESRD (glomerular filtration rate [GFR] <15 mL/min) who underwent RN for suspected malignant SRM from 2000-2018. Group 1 consisted of patients who underwent RN after transplant; group 2 underwent RN prior to transplant, and group 3 underwent RN without subsequent transplant. Dominant tumor size and histopathological characteristics, recurrence, and survival outcomes were compared between groups. Chi-squared and Mann-Whitney U tests were used to compare categorical and continuous baseline and histopathologic characteristics, respectively. Univariate analysis and log rank test were used to compare RCC recurrence rates. Results: We identified 34 nephrectomies in group 1, 27 nephrectomies in group 2, and 70 nephrectomies in group 3. Median time from transplant to SRM radiological diagnosis in group 1 was 87 months, and three months from diagnosis to nephrectomy for all groups. There were no statistically significant differences between pathological dominant mass size, histological subtype breakdown, grade, or stage between the groups. Rates of benign histology were similar between the groups. Univariate analysis did not reveal a statistically significant difference in recurrence-free survival between the groups (p=0.9). Conclusions: Patients undergoing nephrectomy before or after transplant for SRM have similar indolent clinicopathological characteristics and low recurrence rates. Our results suggest that chronic immunosuppression does not adversely affect SRM biology.