OBJECTIVE: To evaluate the success and complications of thermal ablation (TA) based on the voluntary, prospective registry of the German Society for Interventional Radiology and Minimally Invasive Therapy (DeGIR) with 303 participating centers from Germany, Austria, and Switzerland. MATERIALS AND METHODS: Registry data from 2018 until 2023 of 1102 patients with small renal tumors (age: 72.5 ± 11.6 years
female: 33.6%, 370/1102) were analyzed. Hospitals with ≥ 20 TAs were considered high-volume centers. Technical success and complication rates between different parameters were compared using the chi-square or Fisher's exact test, p <
0.05 was considered statistically significant. RESULTS: Patients were most frequently treated with radiofrequency ablation (RFA, 43.6%, 481/1102), then microwave ablation (MWA, 41.9%, 462/1102) or cryoablation (13.3%, 147/1102). Technical success for heat-based TA (RFA&MWA) was 94.3% (893/947), for cryoablation 97.3% (143/147). RFA&MWA was significantly more successful in lesions ≤ 3 cm (96.1%, 567/590) compared to 3-4 cm lesions (89.8%, 97/108
p = 0.005). In patients treated with cryoablation, no significant differences between sizes could be found (≤ 3 cm: 97.9%, 94/96
3-4 cm: 85.7%, 12/14
p = 0.078). Complication rate was significantly higher in RFA&MWA of lesions 3-4 cm compared to ≤ 3 cm (≤ 3 cm: 3.9%, 23/590
3-4 cm: 11.1%, 12/108, p = 0.002), while no significant differences were seen regarding cryoablation (≤ 3 cm: 1.0%, 1/96
3-4 cm: 0.0%, 0/14
p = 1.000). CONCLUSIONS: In this exploratory analysis of the DeGIR registry, percutaneous TA of small renal masses is technically feasible with low complication rates. Heat-based TAs seem to have lower success rates and higher complication rates in larger tumors. Cryoablation could potentially be a safe alternative for 3- to 4-cm-sized tumors. KEY POINTS: Question How effective is renal thermal ablation (TA) in terms of treatment success and complication rates? Findings In contrast to cryoablation, heat-based thermal ablation has lower success and higher complication rates in tumors measuring 3-4 cm compared to tumors <
3 cm. Clinical relevance Thermal ablation is not influenced by the need for additional techniques such as cooling, protective organ displacement, or temporary vessel occlusion. For small renal tumors, TA is an effective and safe treatment option. Cryoablation could be beneficial in larger tumors.