Percutaneous microwave ablation (MWA) of renal tumours: intermediateterm results and usefulness of R.E.N.A.L. scoring for predicting outcomes and complications

Purpose: We evaluated intermediate-term results after MWA of Renal tumours and retrospectively applied the R.E.N.A.L. (radius, exophytic/endophytic, nearness to collecting system, anterior/posterior and location relative to polar lines) score to renal tumours to determine whether this score correlates with oncological outcomes and complications. Methods and Materials: Sixty patients with 60 lesions were treated via percutaneous MWA from May 2008 to July 2014. Follow-up (mean 25.7 months, range 3-72 mo). was obtained performing Contrast Enhanced Computed Tomography (CECT) at 1, 3, 6, 12 and 24 months. Technical success (TS), primary technical effectiveness (PTE), secondary technical effectiveness (STE), local tumour progression rate (LTPR), cancer specific survival rate (CSSR), overall survival (OS) were recorded. R.E.N.A.L. tumour scores were recorded to analyze the association between the score and ablation treatment outcomes and complications. Results: Technical success was 100%, PTE was 95% (3 residual lesions were identified), STE was 100%, CSSR at 1-, 2- and 3-year was 100%; OS at 1-, 2- and 3-year was 100%, 93% and 100%. No major complications were observed. The mean ± SD R.E.N.A.L. nephrometry score of all ablated tumours was 7.7 ± 1.9 (range 4-11). Mean nephrometry score was 7.6 ± 2.2 for tumours with local treatment failure (3/60). Patients with minor complication (5/60) had a mean score of 9.5. Conclusion: In the intermediate term, percutaneous MWA appears to be a safe and effective treatment for renal tumours. The R.E.N.A.L. nephrometry score could correlate with treatment efficacy and complications but further studies are needed to confirm our experience.