Stereotactic Body Radiotherapy for Stage I Renal Cell Carcinoma: National Treatment Trends and Outcomes Compared to Partial Nephrectomy and Thermal Ablation

PURPOSE: To assess use of stereotactic body radiotherapy (SBRT) for stage I renal cell carcinoma (RCC) and compare outcomes with thermal ablation and partial nephrectomy (PN). MATERIALS AND METHODS: The 2004-2015 National Cancer Database was investigated for histopathologically proven stage I RCC treated with PN, cryoablation, radiofrequency (RF) or microwave (MW) ablation, or SBRT. Patients were propensity score-matched to account for potential confounders, including patient age, sex, race, comorbidities, tumor size, histology, grade, tumor sequence, administration of systemic therapy, treatment in academic vs nonacademic centers, treatment location, and year of diagnosis. Overall survival (OS) was evaluated with Kaplan-Meier plots, log-rank tests, and Cox proportional hazards models. RESULTS: A total of 91,965 patients were identified (SBRT, n = 174; PN, n = 82,913; cryoablation, n = 5,446; RF/MW ablation, n = 3,432). Stage I patients who received SBRT tended to be older women with few comorbidities treated at nonacademic centers in New England states. After propensity score matching, a cohort of 636 patients was obtained with well-balanced confounders between treatment groups. In the matched cohort, OS after SBRT was inferior to OS after PN and thermal ablation (PN vs SBRT, hazard ratio [HR] = 0.29, 95% confidence interval [CI] 0.19-0.46, P < .001; cryoablation vs SBRT, HR = 0.40, 95% CI 0.26-0.60, P < .001; RF/MW ablation vs SBRT, HR = 0.46, 95% CI 0.31-0.67, P < .001). Compared with PN, neither cryoablation nor RF/MW ablation showed significant difference in OS (cryoablation vs PN, HR = 1.35, 95% CI 0.80-2.28, P = .258; RF/MW ablation vs PN, HR = 0.64, 95% CI 0.95-2.55, P = .079). CONCLUSIONS: Current SBRT protocols show lower OS compared with thermal ablation and PN, whereas thermal ablation and PN demonstrate comparable outcomes.