3377 - Analysis of SBRT for Oligoprogressive Renal Cell Carcinoma Lung Metastases: Impact on Distant Control, Systemic Therapy, and Survival Outcomes

Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) has emerged as a strategy to overcome relative radioresistance of renal cell carcinoma (RCC) through ablative dosing. In oligoprogressive RCC, SBRT may delay systemic therapy (ST) escalation and reduce cumulative toxicity. We evaluated outcomes of SBRT for lung metastases in oligoprogressive RCC and assessed prognostic factors that may aid in patient selection for SBRT.

Materials/Methods: We retrospectively reviewed patients treated with SBRT for lung oligometastasis from renal cell carcinoma between 2007 and 2024. A mutlivariable binary logistic regression model was used to evaluate the impact of patient characteristics, tumor features, and treatment factors on time to next metastasis and overall survival.

Results: Seventy-two patients were identified, with a median follow-up of 35 months and median overall survival (OS) of 32.69 months. Sixty-one percent of patients were alive at the time of analysis. Patient characteristics included: female (n = 12), median age 67.8 years, and median Karnofsky Performance Status (KPS) of 90. The majority of patients (93%) had clear cell histology. Treatment intent varied and included oligoprogression off systemic therapy (n=45), oligoprogression continuing same systemic therapy (n=21), and consolidation to stop systemic therapy (n=6). Local control (LC) was 97%, with 1-year LC and disease-free survival of 100% and 47%, respectively. Among all patients with progression (n=47), the median time to next metastasis (TTNM) was 8 months. While at 6 months, IMDC intermediate risk classification showed a trend toward increased risk of metastasis (OR 9.87, p=0.08), compared to favorable risk, no clinical or pathologic variables (age, gender, IMDC group, tumor size, presence of necrosis, synchronous versus metachronous presentation, or indication for SBRT) correlated with risk of additional metastasis at 12 months. IMDC intermediate risk classification was the only variable correlated with higher OS (p=0.0011) compared with favorable risk.

Conclusion: SBRT for lungametastases in oligoprogressive renal cell carcinoma results in excellent local control, consistent with broader literature supporting SBRT. We were unable to identify statistically significant associations between classic patient, tumor or treatment variables and prolonged TTNM. These results may potentially reflect a pre-existing selection in determining candidacy for SBRT as a stronger driver in outcome than classic disease-specific predictors.