Introduction: The objective of this study was to evaluate the impact of the histology at pre-procedure biopsy and the type of energy used for local tumor ablation (LTA, including Radiofrequency ablation [RFA], Cryoablation [Cryo], Microwave ablation [MW]) on long-term oncologic outcomes in patients with cT1a renal masses. Methods: We retrospectively evaluated 650 patients treated with LTA for cT1a renal tumors at 4 European tertiary centers. Patients lost to follow-up were excluded from the analysis, leading to a final population of 574 patients. Individuals with cT1a renal mass unfit for surgery were primary scheduled for LTA in each center. Before LTA a percutaneous biopsy of the renal mass was performed to achieve the histology of the tumor. Patients were treated with percutaneous RFA, Cryo or MW according to the technique available in each center. Outcome of interest were followings: recurrence free survival (R-FS) and cancer specific mortality-free survival (CSM-FS) in patients with malign histology. Kaplan-Meier curves were used to investigate 5-years RFS and CSM-FS according to the histology at biopsy and the technique used for ablation. Multivariable Cox’s proportional hazard regressions were performed to identify predictors of R-FS. Results: Overall, 197 (34%), 241 (42%) and 136 (24%) patients were treated with RFA, Cryo and MW, respectively. Median age at treatment was 68 years (IQR 60-76). Overall, 350 (60%) patients had ASA score =3. Median tumor size was 2.2 (IQR 1.7-3) cm. At biopsy, 330 (57%), 86 (15%), 9 (1,6%), 87 (15%), 9 (1.6%), 6 (1%) and 47 (8.2%) tumors were clear cell carcinoma, papillary, chromophobe, oncocytoma, angiomyolipoma, mixed tumors and non-diagnostic, respectively. All the procedures were complete, with no sign of residual tumor at the 24 hours imaging. During a median follow-up of 60 months (IQR 35-87), 67 (12%) patients experienced local recurrence, while 20 patients (3.5%) experienced systemic recurrence. The 5-years R-FS was 65%, 88% and 82% (p < 0.001) and the 5-years CSM-FS was 96%, 94% and 98% (p=0.8) for patients treated with RFA, Cryo and MW, respectively; according to the histology, the 5-years R-FS was 73%, 89%, 74%, 62%, 96% (p=0.003) and the 5-ys CSM-FS was 94%, 100%, 100%, 100%, 100% (p=0.19) for clear cell carcinoma, papillary, chromophobe, mixed tumors and non-diagnostic histology, respectively. At multivariable analysis, clinical size (HR 1.51, CI 1.17-1.95, p=0.001), papillary histology (HR 0.27, CI 0.09-0.64, p=0.007) and MW ablation (HR 0.45, CI 0.22-0.88, p=0.02) were independent predictors of R-FS. Conclusions: Percutaneous LTA is a safe and effective approach to small renal masses in patients unfit for surgery. MW ablation, smaller clinical size and papillary histology are associated with lower risk of recurrence at 5-year. SOURCE OF Funding: None.
