Patients with larger (T1b, >4 cm) renal cell carcinoma (RCC) not suitable for surgery have few treatment options as thermal ablation is less effective in this setting. We hypothesize that stereotactic ablative radiotherapy (SABR) represents an effective, safe, and nephron-sparing alternative for large RCC.
Individual patient data from nine institutions in [BLINDED FOR REVIEW] were pooled. Patients with T1a tumors, M1 disease, and/or upper tract urothelial carcinoma were excluded. Demographics, treatment, oncologic and renal function outcomes were assessed using descriptive statistics. Kaplan-Meier estimates and univariable and multivariable Cox proportional hazards regression were generated for oncologic outcomes.
Ninety-five patients were included. Median follow-up was 2.7 years. Median age was 76 years, median tumor diameter was 4.9cm and 81.1% had ECOG performance status of 0-1 (or KPS ≥70%). In patients for whom operability details were reported, 77.6% were defined as inoperable as determined by the referring urologist. Mean baseline estimated glomerular filtration rate (eGFR) was 57.2mL/min (mild-to-moderate dysfunction) with 30% of the cohort having moderate-to-severe dysfunction (eGFR <45mL/min). Following SABR, eGFR decreased by 7.9mL/min. Three patients (3.2%) required dialysis. Thirty-eight patients (40%) had a grade 1-2 toxicity. No grade3-5 toxicities were reported. Cancer-specific survival (CSS), overall survival (OS), and progression free survival (PFS) at 2 years were 96.1%, 83.7% and 81.0% and at 4 years were 91.4%, 69.2%, 64.9%, respectively. Local, distant and any failure at 4 years were 2.9%, 11.1% and 12.1% (cumulative incidence function with death as competing event). On multivariable analysis, increasing tumor size was associated with inferior CSS (HR per 1 cm increase: 1.30; p<0.001).
SABR for larger RCC in this older, largely medically inoperable cohort demonstrated efficacy, tolerability and had modest impact on renal function. SABR appears to be a viable treatment option in this patient population.

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