ESTRO 2025 - Abstract Book

S4039

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2025

Treatment tolerability assessment included determining the incidence and severity of early and late radiation induced toxicity based on CTCAE 5.0 and IPSS scales. Indicators were controlled before and immediately after treatment course completed as well as 3, 6 and 12 months after SBRT. PSA test and pelvic ultrasound data were also monitored. Standard descriptive statistics was used to analyze the data. Results: By now of the 17 patients underwent SBRT 14 patients had follow-up more than 3 months, 11 patients – more than 6 months, 9 patients – more than 12 months. The median of patients’ age at the time of RT was 72.5(67.3; 73.2) years. The median prostate volume was 33(28.7; 43.0) ml, the median PTV was 52.7(43.7; 71.7) ml. Immediately after treatment course and 3 months after SBRT patients noted only the symptoms of grade 1 cystitis. In 6- and 12-month follow-up the patients did not report any symptoms of bladder or rectum toxicity. The median of IPSS decreased from 12(7;15) points to 4(2;5) points after SBRT (Table 1). According to the pelvic ultrasound, no evidence of the PCa relapse was identified.

Conclusion: SBRT showed to be an effective and safe method of low- and intermediate-risk PCa treatment. Implementation of ETBPS in combination with CBCT for PCa RT provides optimal target position control and allows SBRT usage without grade 2 or higher radiation toxicity development. Further study of the PCa SBRT using ETBPS will clarify and expand the indications for this method.

Keywords: prostate cancer SBRT, electromagnetic tracking

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Poster Discussion Evaluation of the imaging tolerance in Proton Therapy for High-Risk Prostate Cancer Thidar Engt Meilian Zheng 1 , Nur Atiqah Binte Samsuri 1 , Adelene Hwee San Boo 1 , Jason Wei Siang Chan 1 , Kah Seng Lew 1 , Andrew Wibawa 1 , Calvin Wei Yang Koh 1 , Hong Qi Tan 1,2 1 Radiation Oncology, National Cancer Centre Singapore, Singapore, Singapore. 2 Oncology Academic Clinical Programme, Duke-NUS Medical School, Singapore, Singapore Purpose/Objective: It is important to maintain the dose coverage in both the primary prostate target and the lymph node clinical target volume (CTV) during the treatment of high-risk prostate patients with proton therapy. In National Cancer Centre Singapore (NCCS), an imaging protocol was developed during the start of the service in June 2023 to guarantee this. This includes first performing a bone match using daily cone-beam computed tomography (CBCT), followed by a primary target matching using gold fiducial markers. The difference between the two matches must be within 5 mm in all the three cardinal directions for the treatment to proceed. However, this tolerance was proposed as a