Kidney function decline in cT1a patients treated with Microwave Ablation versus Partial Nephrectomy.

Background: Microwave ablation (MWA) is an emerging treatment modality for clinical T1a (cT1a) small renal masses (SRM) with studies showing it has comparable oncological outcomes to partial nephrectomy (PN). However, more research is needed to the impact of each treatment on kidney function decline.

Objective: To compare the progression of kidney function decline in patients with cT1a SRM treated with MWA or PN.

Methods: This study included prospective data on patients treated between 2015-2021 with kidney function data collected from 2015-2024 from a single institutional database. Three outcomes for kidney function decline were examined: 30% decline in estimated glomerular filtration rate (eGFR) compared to pre-treatment, chronic kidney disease (CKD) upstaging compared to pre-treatment and eGFR <60 mL/min/1.73m², and the composite endpoint of the previous two events. Cox proportional hazards models were used to compare outcomes between the two treatments.

Results: Among 97 MWA and 49 PN included, MWA patients were older, had lower baseline eGFR, and higher rates of CKD prior to treatment. Univariate Cox proportional hazard model showed treatment modality was not significantly associated with reaching kidney decline endpoints. After adjusting for patient characteristics (age, race, baseline eGFR, Charlson Comorbidity Index), only baseline eGFR was associated with reaching kidney function endpoints.

Conclusion: There was no statistically significant difference in kidney function decline between PN and MWA treatments for cT1a SRM. After adjusting for patient factors, the higher hazard for MWA was attenuated.