A Trifecta-Based Evaluation of Patients Treated with Percutaneous Thermal Ablation of Small Renal Masses

Scoring metrics are important to compare outcomes of different percutaneous treatments for small renal masses (RMs). The concept of trifecta (no complications, kidney function preservation, and absence of local recurrence) has been recently introduced in percutaneous thermal ablation of RM. In this context, previous studies have shown that cryoablation (CA) and microwave ablation (MWA) have similar outcomes. We aimed to validate the trifecta in CA and MWA and factors associated with treatment success. A retrospective comparative analysis of two cohorts was carried out on 190 consecutive patients with RMs treated using percutaneous CA or MWA. Nephrometry scores described RM complexity. Postoperative complications were categorized according to the Clavien-Dindo system. Glomerular filtration rate (GFR) at the last follow-up was calculated through the chronic kidney disease-epidemiology collaboration (EPI) formula, whereas detection of contrast enhancement during follow-up defined local recurrence. Last, trifecta was defined by the combination of no major (Clavien >2) complications, estimation of GFR (eGFR) decline <10%, and absence of local recurrence. Descriptive statistics and logistic regression models tested the association between predictors and trifecta achievement. Factors associated with recurrence were compared by the log-rank test. Of 175 patients, 121 (69.1%) and 54 (30.8%) patients underwent CA and MWA, respectively. Median (interquartile range [IQR]) age and RM diameter were 75 years (66-80) and 2.4 cm (1.8-3.0). The CA group had a lower preoperative GFR but also had a lower rate of comorbidities (both p = 0.01). Other demographics and tumor characteristics were comparable between groups. In the CA and MWA groups, major complications occurred after 1.6% and 4.8% of procedures (p = 0.33), whereas an eGFR decline >10% was found in 31.5% and 38.8% of cases (p = 0.40), respectively. Similarly, in the CA and MWA groups, at a median follow-up of 21 (8-39) and 24 (9.5-36) months, local recurrence was observed after 10 (8.3%) and 5 (9.3%) cases (p = 0.78), trifecta was accomplished after 72 (59.5%) and 32 (59.3%; p = 1.00) procedures, respectively. Of note, recurrence-free survival (RFS) was comparable among groups (p = 0.57). Moreover, trifecta achievement was comparable when stratifying for demographics and tumor characteristics in the whole cohort and in the CA group (p > 0.05). Conversely, logistic regression showed a lower odds ratio (OR) of trifecta for lesions close to renal collecting system treated by MWA, even when accounting for maximum diameter and preoperative GFR (OR 0.21, confidence interval 0.60-0.72, p = 0.010). Of note, this factor was also associated with a significantly lower RFS (log-rank p = 0.002). Both percutaneous CA and MWA of RM can safely accomplish good oncological outcomes while preserving renal function. Approximately 6 out of 10 patients achieved trifecta after each procedure. Patient selection should account for tumor proximity to the collecting system, as this factor seems to impact the outcomes of MWA.