Introduction: Thermal ablation (TA) is a well-accepted minimally invasive treatment option for patients with small renal masses (SRM).  As a high-volume TA centre, we report our contemporary outcomes data and factors leading to treatment failure.

Methods: A retrospective chart review of patients undergoing TA in Saskatoon, Saskatchewan between 2012-2019 was conducted.  Patient and tumor characteristics were analyzed using measures of central tendency.  Treatment outcomes and comparison of modalities were analyzed using Wilcoxon test, and chi-square tests.

Results: The study cohort had a median patient age of 69 years (range=36-73 years) and median tumor diameter of 2.5 cm (range=1-6 cm).  99 microwave ablation (MWA) and 95 radiofrequency ablation (RFA) were successfully performed during the study period with only one attempted procedure not being technically possible.  The procedural and post-procedural complication rate (above Clavien-Dindo Class 2) was 1%.  Over a mean follow-up of 19.9 months (range=0-74 months), 8.8% had residual tumor (detected on first imaging study after TA) and 2.6% developed more remote tumor recurrence.   Residual tumor post-TA was associated with larger tumors (p<0.0001) and treatment with MWA (p=0.039), however MWA-treated tumors were larger (2.79 cm vs. 2.41 cm, p=0.02) and had a higher biopsy positive rate for cancer (56.5% vs. 47.4%, p=0.034).  In those who required a repeat procedure, 88.2% were successfully salvaged with additional TA.

Conclusions: TA is a safe and effective treatment option for patients with SRM.  Those with residual disease had larger tumors and were more likely to be treated with MWA, however these patients could be salvaged with more TA in the vast majority of cases.