ESTRO 2025 - Abstract Book

S1899

Clinical - Urology

ESTRO 2025

818

Digital Poster Tumour Response Assessment with PSMA-PET Scan (PSMA Scan) Following Stereotactic Ablative Radiation Therapy (SABR) for Renal Cell carcinoma (RCC). Tee Sin Lim 1,2 , Tarmara Fogarty 1 , Richard Gaucci 3 , Matthew Lim 4 , Dickon Hayne 5,6 1 GenesisCare, Fiona Stanley Hospital, Murdoch, Australia. 2 UWA Medical School, University of Western Australia, Perth, Australia. 3 Department of Nuclear Medicine, Fiona Stanley Hospital, Murdoch, Australia. 4 Curtin Medical School, Curtin University, Bentley, Australia. 5 Depart of Urology, Fiona Stanley Hospital, Murdoch, Australia. 6 Department of Surgery, University of Western Australia, Perth, Australia Purpose/Objective: Our primary objective was to investigate the role of PSMA PET in monitoring treatment response in patients who received SABR for RCC. A secondary objective was to evaluate renal function following SABR. Material/Methods: We present a retrospective series of 20 patients who underwent 22 courses of SABR to the kidney at Genesiscare, Fiona Stanley Hospital (FSH), Perth, Australia. PSMA PET was performed prior to SABR, and at multiple time points following SABR to assess treatment response. Secondary outcomes included PSMA PET parameters, tumour pathology and renal function. Results: Between June 2021 and June 2024, a total of 30 patients with localized RCC were referred for SABR. All cases were discussed in the Genitourinary Multidisciplinary Team meeting at Fiona Stanley Hospital (FSH) and were deemed medically or surgically unsuitable for partial or radical nephrectomy. Of these, 20 patients met the inclusion criteria, undergoing a total of 22 courses of SABR. Diagnostic biopsies were performed on 21 tumors prior to treatment, with 14 identified as clear cell RCC and 7 as papillary RCC. Baseline PSMA PET scans were conducted for 20 of the SABR treatments. Four tumors did not demonstrate PSMA binding, and all of these were papillary RCC. Among the 16 PSMA-binding tumors, 3 showed a complete response on their first post-SABR PSMA PET, 9 displayed a partial response, and 2 had stable disease. Two tumors have yet to undergo post-treatment PSMA PET evaluation. Conclusion: PSMA PET is a promising imaging modality for evaluating treatment response following SABR in RCC, especially for the clear cell subtype. However, prospective studies are needed to further clarify its role and enhance its clinical application. References: 1. Siva S, Ali M, Correa R, et al. 5-year outcomes after stereotactic ablative body radiotherapy for primary renal cell carcinomas: an individual patient data meta-analysis from IROCK (the International Radiosurgery Consortium of the Kidney). Lancet Oncol. 2022;23:1508-16. 2. Raj R, Upadhyay R, Wang S, Singer E, Dason S. Incorporating stereotactic ablative radiotherapy into the multidisciplinary management of renal cell carcinoma. Curr Oncol. 2023 Dec;30(12):10283-10298. 3. Siva S, Callahan J, Pryor D, Martin J, Lawrentschuk N, Hofman M. Utility of (68)Ga prostate specific membrane antigen – positron emission tomography in diagnosis and response assessment of recurrent renal cell carcinoma. J Med Imaging Radiat Oncol. 2017 June;61(3):372-8 Keywords: Kidney, cancer, PSMA