263 - Stereotactic Radiation for Systemic Therapy-Naïve Oligometastatic Kidney Cancer: Final Results of a Phase IIb Trial
Presenter(s)
R. Assadi1, A. Christie2, V. Puliyadi1, A. Garant1, H. Hammers3, W. Arafat3, K. Courtney3, D. J. Sher1, C. Ahn2, S. Cole3, J. Brugarolas3, R. D. Timmerman1, and R. Hannan1; 1Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, 2Kidney Cancer Program, Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX, 3Department of Internal Medicine, Hematology Oncology, University of Texas Southwestern Medical Center, Dallas, TX
Purpose/Objective(s): Treatment regimens for oligometastatic renal cell carcinoma (RCC) are not standardized and often cause significant toxicity. This study evaluates the efficacy and tolerability of sequential stereotactic ablative radiotherapy (SAbR) as first-line treatment in oligometastatic RCC patients.
Materials/Methods: This prospective, single-arm, phase IIb trial enrolled systemic therapy-naïve oligometastatic RCC patients. Eligible patients were =18 years of age, had pathologically proven RCC, were favorable or intermediate IMDC risk group, and had =3 extracranial metastases that were all amenable to SAbR. All lesions were treated with SAbR, treatment regimens included: =25Gy x1 fraction, =12Gy x 3 fractions, or =8Gy x 5 fractions. Sequential treatment was permitted for new lesions if modified progression free survival (mPFS) criteria were not met (>3 new metastases, >6 total metastases, metastasis not amenable to SAbR, local failure at SAbR-treated site, or brain metastasis). The primary endpoint was delay of time to systemic therapy (TTST) by one year in at least 60% of patients, with TTST defined as the time from the first day of SAbR to initiation of systemic therapy. Treatment was guided by radiographic imaging performed at three-month intervals. Secondary endpoints included mPFS, PFS on subsequent systemic therapy (PFS-ST), overall survival (OS), cancer-specific survival (CSS), local control (LC), toxicity, and health-related quality of life (HRQoL).
Results: The trial enrolled 23 patients with SAbR administered to 69 total lesions. The median follow-up was 45 months (interquartile range 26-57). The median TTST was 55.6 months, with 91% of patients free from systemic therapy at 1 year (95% CI: 69.5, 97.8). SAbR achieved 100% LC and the median mPFS was 40 months. Median PFS-ST was 5.7 months. Three-year OS and CSS were 68.7% (95% CI: 45.3, 83.8) and 87.0% (95% CI: 64.8, 95.6), respectively. There was one grade =3 adverse event possibly related to SAbR. HRQoL assessments showed no significant changes over time.
Conclusion: Sequential SAbR delayed initiation of systemic therapy in selected oligometastatic RCC patients, achieving durable disease control and preserving quality of life. SAbR may offer a safe alternative as first-line treatment in oligometastatic RCC. These findings warrant validation in a prospective randomized investigation.