Assessing outcomes in probe ablative therapies for small renal masses

The increasing incidence of renal-cell carcinoma can be largely attributed to the increased detection of small renal masses (SRMs) via abdominal imaging. These lesions tend to have a slow rate of growth and low malignant potential, and hence, minimally invasive treatments and active surveillance have been developed for these low-risk tumors to minimize treatment-related morbidity. Radiofrequency ablation and cryotherapy are the principal less-invasive approaches, and their initial oncologic efficacy and complication profiles have been favorable. Suboptimal definition of the relevant outcomes of treatment, a dearth of prospective and randomized data, and relatively short follow-up in the context of the natural history of SRMs pose challenges in the assessment of the efficacy and outcomes of thermal ablation of renal-cell carcinoma. Better pretreatment characterization of the biology of these tumors, more effective real-time treatment monitoring, and standardization of outcome definitions and follow-up are needed to better clarify the effectiveness and role of these treatments. This review highlights these potential pitfalls in the assessment of outcomes of probe ablation of SRMs.