S1195
Clinical - Urology
ESTRO 2026
Digital Poster 1806 SBRT with peri-rectal spacer for low or
had PSMA PET/CT stating with either [68Ga]Ga-PSMA or [18F]F-DCFPyL tracers. Prostate contours were delineated on the CT component of the PET/CT scans using MIM Maestro software, and PSMA avid intra- prostatic lesions were identified. Standardized uptake value (SUV) metrics (SUVmax, SUVmean) were correlated with predicted 10-year distant metastasis risk and ST-ADT benefit from the Artera-AI Prostate- Test. Results: 109 patients with IRPC were included. Mean age was 74 years (range 59-87). Staging was T1a (1%), T1c (19%) T2a (40%), T2b (24%), and T2c (16%). ISUP grade was 2 in 47% and 3 in 53%. Mean PSA was 6.3 ng/mL (range 1.2–20); 37% had favourable and 63% unfavourable risk disease. Median predicted 10yr risk of distant metastases was 3.1% (range 1.1-8.4). 52 (48%) had 1 lesion detected on PSMA/PET/CT, 43 (39%) had no lesion and 14 (13%) had more than 1 lesion. Mean SUVmax for detected lesions was 15.6 (2.4 - 97.0) and mean SUVmean was 2.4 (0.3-8.5). SUVmax was showed low-moderate correlation with 10yr risk of distant metastases (r=0.25, p<0.01), while SUVmean showed no significant correlation (r=0.11, p=0.26). Mean SUVmax was significantly higher in patients predicted to benefit from ST-ADT compared with those not predicted to benefit (21.3 vs 12.2, p < 0.01). The optimal SUVmax threshold for ST-ADT prediction was 16.8 (sensitivity 40%, specificity 86%). Conclusion: PSMA PET/CT findings showed mixed correlation with the Artera-AI Prostate-Test. Higher SUVmax values demonstrated a weak correlation with metastasis risk, but SUVmax ≥ 16.8 was associated with an 86% likelihood of Artera-AI–predicted ST-ADT benefit. PSMA PET/CT may complement the Artera-AI Prostate-Test in guiding treatment decisions for IRPC patients undergoing radiotherapy. References: 1. Krauss DJ et al. Dose-escalated radiotherapy ± short- term androgen deprivation for intermediate-risk prostate cancer: Phase III multi-institutional trial. J Clin Oncol. 2023;41:3203–16.2. Spratt DE et al. Artificial intelligence predictive model for hormone therapy use in prostate cancer. NEJM Evid. 2023;2:EVIDoa2300023.3. Karpinski MJ et al. Combining PSMA-PET and PROMISE to redefine stage and risk in prostate cancer: multicentre retrospective study. Lancet Oncol. 2024;25:1188–201.4. Wegener E et al. AI-driven biomarker to inform shared decisions for ADT in prostate radiotherapy: ASTuTE protocol. BMC Cancer. 2025;25:250. doi:10.1186/s12885-025- 13622-1. Keywords: prostate cancer, PSMA PET, biomarkers
intermediate risk prostate cancer in Hong Kong: early institutional toxicity and patient reported outcomes Philip Y Wu 1 , William WL Wong 1 , Hing Ming Hung 1 , Kelvin YC Zheng 1 , Ka Ho Tse 1 , Jeffrey Man Hin Yu 2 , Michael TY Kam 1 , Tsz Chim Liu 1 , Elki SN Cheung 1 , Kuen Chan 1 1 Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong, Hong Kong. 2 Department of Surgery, Pamela Youde Nethersole Eastern Hospital, Hong Kong, Hong Kong Purpose/Objective: Stereotactic body radiotherapy (SBRT) is safe and effective for low or intermediate-risk prostate cancer1, and has been increasingly adopted worldwide. The use of peri-rectal spacer has shown to reduce gastrointestinal toxicity in conventional or moderately- hypofractionated radiotherapy2-3, yet its value in SBRT is not well defined. The current study aims to provide real-world evidence on early clinical and patient-reported outcomes of prostate cancer SBRT with peri-rectal spacer. Material/Methods: Consecutive patients with National Comprehensive Cancer Network low or intermediate-risk prostate cancer who completed SBRT between January 2022 and September 2025 at a single institution in Hong Kong were included in this retrospective study. Patients received 5 fractions of 7.25 Gy over 2 weeks to the prostate (and proximal seminal vesicles in intermediate-risk), delivered by volumetric modulated arc therapy. Peri-rectal spacer implant was performed before MR simulation. Image-guidance consisted of intra-prostatic fiducial markers matching and intra- fractional tracking, in addition to cone beam CT. Androgen-deprivation therapy was not permitted. Primary outcomes were clinician-assessed toxicity graded by Common Toxicity Criteria for Adverse Events (version 5.0), and health-related quality of life (HRQOL) measured by the Expanded Prostate Cancer Index Composite (EPIC-26) and The 5-level EQ-5D version (EQ-5D-5L), which were prospective collected. Results: Forty-three patients were identified. 77% had favourable intermediate-risk disease. The median baseline for prostate volume was 51.5mL (42.8, 60.9 (IQR)), PSA 7.8 ng/mL (5.6, 9.9), and IPSS 6 (4, 10) (Table 1). Median follow-up was 18.4 months. The incidence of acute toxicities was 20.9%, 2.3%, and 0% for grade 1, 2, and 3 gastrointestinal events, respectively, and 67.4%, 11.6%, and 2.3% for genitourinary events. The cumulative incidence of grade 1 and 2 late gastrointestinal toxicities was 30.3% and 3.0%,
Made with FlippingBook - Share PDF online