ESTRO 2025 - Abstract Book

S2053

Clinical - Urology

ESTRO 2025

3504

Digital Poster Single centre experience of using stereotactic ablative body radiotherapy (SABR) to treat primary renal cell carcinoma on the Cyberknife® Machine Riya Patel 1 , Julie Duong 2 , Prasana Nariyangadu 1 , Nihal Shah 1 , Anup Vinayan 1 , Suraiya Dubash 1 , Robert Hughes 1 1 Mount Vernon Cancer Centre, Mount Vernon Cancer Centre, London, United Kingdom. 2 Princess Margeret Hospital, Princess Margaret, Toronto, Canada Purpose/Objective: SABR is an emerging treatment option for patients with primary renal cell carcinoma (RCC) who are not fit for surgical resection. We report our experience of SABR using the Accuray Cyberknife ® system to treat RCC. Material/Methods: A prospective database of patients undergoing SABR for RCC has been maintained between 2019-2024. Toxicity and outcome data was recorded using CTCAEv.5.0 at 6 weeks post treatment and then at 6-month intervals. CT scans and renal function blood tests were repeated at 6 monthly intervals. Results: 19 patients with biopsy proven RCC were treated using SABR. The median age was 72 years (range 59-86) with a median follow-up of 18 months (range 1-30 months). Median tumour size was 4cm (1.4-5.6cm) 12 were left sided and 7 right sided. Prescription doses and organ at Risk (OAR) doses are reported in table 1.

The treatment was well tolerated in all patients. The most experienced side effects post treatment at 6 weeks were grade 1 fatigue, nausea and pain. 1 patient experienced transient grade 2 pain. No residual toxicities were recorded at 6 months with a return to baseline function. There was no grade 3 or grade 4 reported toxicities. One patient died of pulmonary embolism 2 months post treatment. Renal function was measured using an estimated GFR. There was a median eGFR reduction of 3ml/ min (-10 to +12) at 6 months and 0.5 ml/ min (-13 to +10) at 12 months showing short term renal function was not significantly impacted following renal SABR. Post treatment CT scans frequently showed transient increases in tumour size at 6 months (40%) and at 12 months (36%) before decreasing or remaining stable (see image 1). The increase in size was felt to represent tissue oedema and subsequent necrosis. Local control was achieved for 94% of patients at 1 year.1 patient developed metastatic disease at 2 months. Median PFS following SABR was 20 months.