Abstract
OBJECTIVES: To assess the safety and efficacy of percutaneous microwave ablation (MWA) of histologically proven T1 renal cell carcinoma (RCC). METHODS: We analysed patients with a histologically proven RCC (≤ 7 cm) treated by MWA from April 2012-April 2018. Primary and secondary efficacy, local tumour recurrence (LTR), morbidity and mortality were reported. Efficacy was defined as no residual tumour enhancement on follow-up imaging 1 month after the first ablation (primary efficacy) and after re-ablation(s) for residual disease (secondary efficacy). Adverse events (AE) were registered by the Clavien-Dindo classification and the common terminology criteria for AE. Univariable and multivariable logistic regression analyses were performed to investigate a relation among pre-treatment factors incomplete ablation and complications. RESULTS: In 100 patients, a total of 108 RCCs (85 T1a and 23 T1b) were treated by MWA. Median size was 3.2 cm (IQR 2.4-4.0). Primary efficacy was 89% (95%CI 0.81-0.94) for T1a lesions and 52% (95%CI 0.31-0.73) for T1b lesions (p < 0.001). Fifteen lesions (7 T1a) were re-ablated for residual disease by MWA in one (n = 13) and two (n = 2, both T1b) sessions resulting in secondary efficacy rates of 99% (T1a) and 95% (T1b, p = 0.352). LTR occurred in four tumours (2 T1a, 2 T1b) after 10-60 months. Six (4%) AEs grade > 3-5 were observed (2 T1a, 4 T1b, p = 0.045). Multivariable analysis showed that mR.E.N.A.L. nephrometry was independently associated with incomplete ablation (p = 0.012). CONCLUSION: Microwave ablation is safe and effective for T1a and T1b RCC lesions with a significantly lower primary efficacy for T1b lesions.