Ablative Therapies versus Partial Nephrectomy for Small Renal Masses – A systematic review and meta-analysis of observational studies

Introduction: The ideal treatment of small renal masses is unclear. Ablative therapies (AT) have been considered as a potential alternative to partial nephrectomy (PN) due to their lower complication rates and similar oncological durability. We conducted a systematic review to compare oncological outcomes in T1a or T1b patients undergoing AT vs PN. Methods: This review is registered on PROSPERO (CRD42020199099). Medline, EMBASE, and Cochrane CENTRAL were searched to identify studies comparing AT and PN. The Cochrane RoB 2.0, ROBINS-I tool and the GRADE approach were used to assess any risk of biases. Results: From 1,748 identified records, 32 observational studies and 1 RCT involving 74,946 patients were included. AT patients were found to be significant older than PN patients (MD 5.70, 95% CI 3.83- 7.58), which highlights the serious confounding bias found in the included studies. Patients who received AT for T1a tumours were found to have significantly worse overall survival (HR 1.64, 95% CI 1.39-1.95), but similar cancer-specific survival (CSS), metastatic-free survival, and disease-free survival to PN. There were significantly fewer post-operative complications (RR 0.72, 95%CI 0.55- 0.94) and smaller decline in renal function post-operatively in AT (MD: -7.42, 95%CI -13.1- -1.70). In T1b patients, while CSS was similar between AT and PN, there is contradicting evidence for other oncological outcomes. Conclusion: AT is potentially non-inferior to PN in the treatment of T1a small renal masses due to similar long-term oncological durability, lower complication rates and better renal function preservation. In T1b patients, long-term high-quality studies are needed to confirm potential benefits of AT.