Comparison of renal functional outcomes of active surveillance and partial nephrectomy in the management of oncocytoma

Purpose: To compare functional outcomes of partial nephrectomy (PN) and active surveillance (AS) in oncocytoma. Methods: Multicenter retrospective analysis of patients with oncocytoma managed with PN or AS (biopsy-confirmed). Primary outcome development of de novo chronic kidney disease (CKD) (eGFR < 60 mL/min/1.73m²). Cox regression Multivariable analysis (MVA) was carried out for predictors of de novo CKD. Linear regression was carried out for factors associated with increasing deltaGFR. Kaplan–Meier Analysis (KMA) was performed to analyze 5-year CKD-free survival. Results: 295 patients were analyzed (224 PN/71 AS, median follow-up 37.4 months). No differences were noted for clinical tumor size (AS 2.6 vs. PN 2.9 cm, p = 0.108), and baseline eGFR (AS 79.6 vs. PN 77, p = 0.9670). Median change in tumor diameter for AS was 0.42 cm. Compared to PN, AS had deltaGFR (−15.3 vs. −6.4 mL/min/1.73m², p < 0.001) and de novo CKD (28.2% vs. 12.1%, p = 0.002). AS patients who developed CKD had higher RENAL score (p = 0.005) and lower baseline eGFR (73 vs. 91.2 mL/min/1.73m², p < 0.001) than AS patients who did not. MVA demonstrated increasing age (OR = 1.03, p = 0.025), tumor size (HR = 1.26, p = 0.032) and AS (HR = 4.91, p < 0.001) to be predictive for de novo CKD. Linear regression demonstrated AS was associated with larger decrease in deltaGFR (B = −0.219, p < 0.001). KMA revealed 5-year CKD survival was higher in PN (87%) vs. AS (62%, p < 0.001). Conclusion: AS was associated with greater functional decline than PN in oncocytoma. PN may be considered to optimalize renal functional preservation in select circumstances. Further investigation into mechanisms of functional decline in oncocytoma is requisite.