Main Session
Sep
29
PQA 06 - Genitourinary Cancer, Gynecological Cancer, and Health Care Access and Engagement
3274 - Skeletal-Related Events after Radiotherapy for Non-Spine Bone Metastases in Renal Cell Carcinoma
Presenter(s)
Harshath Gupta, MD - MD Anderson Cancer Center, Houston, TX
H. Gupta1, P. Pandey1, M. A. Sanchez1, D. R. Grosshans1, M. P. Mitchell1, P. Lin2, R. Satcher2, S. Patel2, J. Bird2, S. Matin3, S. Prajapati1, L. Colbert1, C. Tang1, B. Moon2, M. Desai4, M. Campbell4, M. K. Rooney1, S. Choi1, P. T. Tran1, and C. J. Hassanzadeh1; 1Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 2Department of Orthopedic Oncology, Division of Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX, 3Department of Urology, Division of Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX, 4Department of Genitourinary Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX
Purpose/Objective(s): Bone metastases occur in one-third of patients with metastatic renal cell carcinoma (mRCC) and cause substantial morbidity from skeletal-related events (SREs). RCC has been considered relatively resistant to palliative RT doses, and optimal management for non-spine metastases remains unclear. We aimed to characterize SREs after RT for non-spine mRCC bone metastases and identify clinical and treatment-related predictors. Materials/Methods: We conducted a retrospective review of polymetastatic RCC patients treated from 2018–2025 with RT to high-risk non-spine bone metastases (long bones, hip/pelvis, shoulder). SRE was defined as pathologic fracture, unplanned surgical intervention, or re-irradiation at a treated site. Analyses were conducted at lesion (time to SRE, pain response) and patient (overall survival [OS]) levels. Pain scores (0–10) were compared pre- and post-RT using paired Wilcoxon signed-rank testing, and shifts in severity (mild 0–3, moderate 4–6, severe 7–10) were assessed with chi-squared tests. Lesion-level predictors were evaluated using univariate Cox regression. OS was estimated by Kaplan-Meier, and time to first SRE was modeled as a time-dependent covariate in Cox regression. Results: Ninety-one patients with 178 treated sites were included (median age 66 [IQR 55–71]; 92% clear cell histology). Median follow-up time from first RT was 47 months (reverse Kaplan–Meier; 95% CI, 33–69). Sites included long bones (76%), hip/pelvis (17%), and shoulder (6%). Most received 2D/3D-CRT (78%) to a median BED10 of 39 Gy (IQR 38–48). Among 91 patients, 35 developed =1 SRE (38%), and 49 deaths occurred, with median OS of 34 months (95% CI 26–43). 45% received a bone-modifying agent (bisphosphonate or denosumab). At the lesion level, 50 sites (28%) had SRE (fracture 40%, procedure 46%, re-RT 8%), and the median time to SRE was 7.8 months (IQR 3.0–12.4) among the 50 sites. Among sites with baseline pain =1 (n=134), median pain improved by 2 points (IQR -4 to -1; p<0.001), with severe pain decreasing from 25% to 11% (p<0.001). Older age was associated with lower SRE risk (HR 0.89 per 5 years; 95% CI 0.79–1.00; p=0.047). Higher BED10 was not associated with SREs (BED10 =60 vs <60 Gy; HR 1.38; 95% CI 0.77–2.47; p=0.28). Undergoing a pre-RT orthopedic procedure trended toward lower SRE risk (HR 0.53; 95% CI 0.27–1.01; p=0.055). Treatment site, bone-modifying agent, and post-RT procedures were not associated with SRE. At the patient-level, SRE showed a trend toward worse OS (HR 1.69; 95% CI 0.93–3.07; p=0.083), similar after age adjustment (HR 1.68; p=0.091). Conclusion: In this contemporary mRCC cohort, SREs occurred in over one-quarter of lesions. RT provided meaningful pain relief, though no dose-response relationship for SRE prevention was observed. SREs were associated with a trend toward inferior survival, highlighting the need for strategies to reduce skeletal morbidity in RCC.