3296 - Clinical Outcomes for Extracranial Oligometastatic Renal Cell Carcinoma Treated with Stereotactic Body Radiotherapy - Institutional Experience

12:45pm - 02:00pm PT

Hall F

Screen: 6

POSTER

Presenter(s)

Justyn Nakashima, DO - Moffitt Cancer Center, Tampa, FL

J. Y. Nakashima¹, J. M. Bryant¹, V. M. Khatri², J. Nenos¹, J. Chahoud³, J. S. Chadha³, M. S. Chatwal³, F. Ionescu³, P. Spiess³, B. Manley³, L. W. Zemp³, A. Rishi², J. F. Torres-Roca¹, P. A. S. Johnstone¹, K. Yamoah¹, and G. D. Grass²; ¹Department of Radiation Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL, ²H. Lee Moffitt Cancer Center and Research Institute, Department of Radiation Oncology, Tampa, FL, ³Department of Genitourinary Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL

Purpose/Objective(s):

Stereotactic body radiotherapy (SBRT) is an effective metastasis directed therapy (MDT) for oligometastatic renal cell carcinoma (OM RCC), improving local control and delaying systemic therapy use in select patients. We aim to evaluate the clinical outcomes in patients that received SBRT for extracranial OM RCC and assess the factors influencing these outcomes.

Materials/Methods:

A retrospective analysis was performed on patients with OM RCC who received SBRT at our institution from 2006-2023. Patient demographics, clinicopathologic features (e.g., BMI, diabetes, IMDC risk, prior treatments), and clinical outcomes were queried. Tumors were classified as oligorecurrence (OR) or oligoprogressive (OP) according to ESTRO-EORTC consensus definitions. Progression free survival (RT-PFS) and local control (LC) were defined from start of SBRT. Kaplan Meier method using log rank test or Cox regression assessed features associated with these endpoints. Logistic regression evaluated predictors of local recurrence. Analyses were performed at the patient and tumor site level.

Results:

We identified 111 patients (187 OM RCC lesions treated). Most patients were male (74%), non-diabetic (70%), underwent radical nephrectomy (85%), and had clear cell histology (85%). The median age at SBRT was 65 and IMDC risk groups (n=90) were favorable (29.7%), intermediate (44.1%), and poor (7.2%). At SBRT, the majority (95.4%) had targeting to a single site and 42.3% were systemic therapy naïve. Pre-SBRT systemic therapy included immunotherapy (24%) and tyrosine kinase inhibitors (42%). The median dose used was 40 Gy (range 16-60) and median fraction was 5 (range 1-8) with a median BED (a/b=3) of 216 (range 39.6-300).

The most common sites treated were bone (50%) and lung (27%). Tumors were synchronous (10%) or metachronous (90%) with 58% and 32% classified as OP and OR, respectively.

At a median follow up from SBRT of 63 months, median RT-PFS was 12.1 months (95% CI 9.3-14.7). Poor IMDC risk (p=0.001) and diabetes (p=0.04) were associated with worse RT-PFS. In OP patients, type of prior systemic therapy was not predictive of RT-PFS (p=0.296). At the tumor site level, the 1- and 2-year LC was 90% and 83% respectively. Sarcomatoid histology was associated with worse LC (p=0.005), while OP lesions (p=0.034), lung metastases (p=0.027), and higher BED (p=0.01) were associated with improved LC. The median time to salvage therapy was 21.4 months and 10.4 months in OR and OP patients, respectively. Only 2 (1.8%) patients developed grade 3 toxicity.

Conclusion:

SBRT is a safe and effective treatment for extracranial OM RCC providing high rates of LC and PFS while delaying the initiation of systemic agents in systemic therapy naïve patients or allowing continued use of the same systemic agent in OP patients. We found that IMDC risk score, presence of diabetes, tumor site, and histology significantly impacted outcomes. Further studies are needed to validate these findings and optimize patient selection for SBRT in OM RCC.