Sterotactic ablative radiotherapy vs. thermal ablation of localized renal cell carcinoma: Is there a preferred...

The diagnosis of renal cell carcinoma (RCC) has increased in incidence due to the frequent cross-sectional imaging. While surgical extirpation is the standard of care, some patients are poor surgical candidates. For these patients, active surveillance is the most prudent choice, however, some patients desire treatment, nonetheless. Percutaneous ablation has been established as a reasonable alternative with acceptable oncologic efficacy and safety. Recent phase II trials have demonstrated the feasibility of sterotactic ablative radiotherapy (SABR) for renal masses in nonsurgical candidates. To delineate which modality should be preferred as second-line therapy, we sought to compare the complication profile, renal function changes, and oncologic efficacy for both treatment options in nonsurgical candidates with localized RCC.

Patients undergoing percutaneous ablation or SABR for localized RCC from 2017 to 2023 were retrospectively reviewed. All patients were deemed nonoperative candidates at the discretion of the treatment team based on Charlson Comorbidity Index (CCI), ASA, and absolute requirement of anticoagulation or antiplatelet status. Primary outcomes were postprocedural complications. Secondary outcomes included renal/GI toxicities, renal function changes, progression-free survival (PFS), and recurrence-free survival (RFS). Variables were compared using Wilcox-rank sum and Fischer's exact tests where applicable. Oncologic outcomes were determined using Kaplan-Meier analysis and compared using the log-rank test.

Seventeen patients underwent SABR, and 139 had percutaneous ablation of localized RCC. The median age (76 vs. 75 years, P = 0.77), body mass index (32.8 vs. 29.9, P = 0.39), and CCI (6 vs. 6, P = 0.59) were similar between the groups. Renal mass size was larger in the SABR group (4.3 vs. 2.4 cm, P < 0.01). The median radiation dose delivered was 42 Gy in 3 fractions. The SABR group (6/17) had a higher overall complication rate compared to the ablation group (18/139) (35.5% vs. 12.9%, P = 0.04), driven by mild gastrointestinal complications. No difference in median follow-up was found (18.6 vs. 20.6 months, P = 0.72). Grade 1 renal/GI toxicity occurred in 23.5% of SABR patients and 17.3% of ablation patients. No higher-grade toxicities were noted in either group. Grade 1 GI toxicity occurred in 3 (17.6%) patients, and grade 2 GI toxicity occurred in 1 (5.9%) patient in the thermal ablation group. The 2-year RFS (100% vs. 94%, P = 0.31) and PFS (100% vs. 96%, P = 0.43) were similar between the groups.

To our knowledge, this is the first single-center study evaluating the comparative efficacy of SABR and percutaneous ablation for RCC in nonsurgical candidates. While demonstrating a higher, albeit minor, complication rate and similar short-term oncologic outcomes, SABR appears to offer a feasible alternative to percutaneous ablation. SABR may be particularly useful in patients that cannot tolerate anesthesia or required positioning, those with renal masses to large for ablation, and in those with unfavorable tumor location, whereby ablation may not be feasible.