Percutaneous Microwave Ablation of Histologically Proven T1 Renal Cell Carcinoma

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.