Peri-operative complications and long-term oncologic outcomes following percutaneous microwave ablation of small renal masses

Introduction: Percutaneous radiological ablative treatment is an important option for the management of small renal masses. We aim to describe oncological outcomes and complications of percutaneous microwave ablation for small renal masses in a regional centre. We carried out a retrospective analysis of a prospective cohort study. Methods: A total of 71 consecutive patients harbouring 68 tumours who underwent percutaneous microwave ablation for small renal masses were included in this study. Exclusion criteria included – metastatic disease at time of treatment, incomplete follow-up, proven benign pathology, and underlying genetic predisposition to renal cell carcinoma. All tumours were T1, with the majority T1a, and four patients (5%) having T1b tumours. Primary outcome measures were 5-year disease-free survival (DFS), 5-year cancer-specific survival (CSS), and complication rate. Results: Median radiological follow-up was 58 months (interquartile range (IQR) = 33–82); median clinical follow-up was 88 months (IQR = 79–102). A total of six patients (8%) had radiological evidence of residual disease on the initial follow-up computerised tomography (CT) scan, with four patients (6%) developing later local recurrence. The median time to local recurrence in these patients was 20 months (IQR = 14–33). DFS at 5 years was 85% (95% confidence interval (CI) = 76–94%); CSS at 5 years was 98% (95% CI = 96–100%). A total of 12 patients (17%) suffered complications with 5 patients (7%) suffering the Clavien–Dindo Grade 4 complications. Complication was more likely in patients who underwent hydrodistension prior to microwave ablation (X 2 = 3.65, p = 0.05). Conclusion: Microwave ablation for T1 tumours produces long-term oncological outcomes comparable to other modalities. However, these outcomes should be considered in the context of the complication rate, particularly when combined with hydrodistension. Level of evidence: 2b