Survival and peri-operative safety outcomes of thermal ablation versus partial nephrectomy for cT1 renal cell cancer at an Australian tertiary institution

Introduction & Objectives: Surgical management of localised renal cancer by partial nephrectomy (PN) is invasive and associated with some morbidity including the development of new onset chronic kidney disease (CKD) or worsening of pre-existing CKD. Therefore, techniques have evolved for treating small renal masses (SRM), with thermal ablation (TA) being reserved for more elderly and comorbid patients where peri-operative surgical risk is high. We describe the first Australian case-series comparing TA to PN in patients with SRM by evaluating peri-operative, renal outcomes, and overall survival.

Methods: The study used a retrospective cohort of patients from the Flinders Kidney Health registry with SRM (<4cm, with nil biopsy or stage T1a renal cancer) who underwent PN or TA from 2009-2021. Patient baseline characteristics, post-operative outcomes, and renal outcomes (eGFR) were collected and compared, with a follow-up period of 12 months. Survival data was measured until December 2021 and plotted using the Kaplan Meier method and treatment groups were compared using a log rank test.

Results: A total of 47 patients underwent treatment of SRM over a 12-year period, with 30 being treated with PN and 17 receiving TA. The average age was 68.2 ± 10.5 years and 40.4% of patients were female. Most patients had prior CKD (83.0%), with significant proportions having hypertension (40.4%) and diabetes (27.7%) as baseline comorbidities. PN patients were younger than those undergoing TA (64.6 vs 74.5 years p<0.001)) and less likely to suffer from diabetes (10 vs 58.8% p<0.0001) or peripheral vascular disease (0 vs 17.6% p = 0.042). Only 1 TA case had bleeding as a complication with 3 requiring readmissions. The absolute number and variety of complications was higher in the PN group, with 21 patients represented. Mean eGFR was similar between treatment subgroups, being 71.7± 18.8 vs 71.4 ± 15.4 at baseline, 64.5 ± 23.0 vs 66.1 ± 16.4 at 3 months, and 67.4 ± 20.6 vs 67.1 ± 17.6 at 1 year follow-up. The mean survival follow up was over 5 years, PN patients were followed up longer and yet had a survival of 84% as seen in Figure 1. The TA cohort had a significantly lower survival (75%) when compared by log rank (p-value 0.015).
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Fig. 1. Comparison of survival between PN and TA. Groups as indicated in the legend. Vertical lines indicate censoring. Number at risk displayed below graph.

Conclusion: In this first Australian retrospective single-centre study of SRM management we find support for the safety of TA as compared to the gold-standard of PN. Although this study is limited by sample size, it adds support for the need of further research into utilisation of TA beyond its indication in high-risk comorbid patients.