S1297
Clinical - Urology
ESTRO 2026
correlation of several RFs from PET with [68Ga]Ga- PSMA-11 and [18F]PSMA-1007 to ISUP grade group (ISUP GG) of individual PCa lesions. Material/Methods: Thirty-five patients with biopsy-proven primary PCa with no evidence of metastatic disease and no prior interventions were prospectively enrolled. All patients underwent PSMA PET-CT with either [68Ga]Ga-PSMA-11 (cohort I, 20 patients) or [18F]PSMA-1007 (cohort II, 15 patients) followed by radical prostatectomy. Specimens were scanned by ex- vivo CT and histologically prepared. On digitized whole-mount prostate sections, PCa areas with different histological morphology were manually defined and sorted into ISUP GG with QuPath. Following segmentation on the ex-vivo CT, the PCa areas were interpolated along the z-axis (from prostate base to apex) to PCahisto-volumes. After co- registration on the PSMA PET-CT, the PCahisto- volumes were manually assigned to their corresponding PCa lesion. Spearman’s test was applied to the correlation of first-order features and the previously reported texture feature QSZHGE (1) to ISUP GG. ROC analysis was performed to obtain the
up to 19Gy, followed by external beam RT (EBRT) of 44Gy in 20 fractions in Arm B. Boost was based on combined information by mpMRI and PSMA-PET. Genitourinary (GU) and gastrointestinal (GI) toxicities were assessed according to CTCAEv5.0. Results: Twenty-five patients were treated with MHRT and 30 patients with HDR-BT+EBRT. After a median FU of 60 months in Arm A the rate of grade 2+ GU and GI toxicity was 28% and 8%. After a median FU of 48 months in Arm B the rate of grade 2+ GU and GI toxicity was 10% and 0% in Arm B, respectively. Two grade 3 GI toxicities were reported in Arm A, caused by multifactorial genesis and interventions. Estimated 4- year-Biochemical-recurrence-free survival is 88% in Arm A and 95% in Arm B with two observed relapses in Arm A und one in Arm B. Median PSA at last FU was 0,23 ng/ml in Arm A and 0,18 ng/ml in Arm B. Conclusion: After a longer FU of median >48 months the HypoFocal Phase II demonstrates safety and efficacy of focal dose-escalated MHRT and HDR-BT+EBRT based on mpMRI and PSMA-PET in intermediate- and high-risk PCa. Particularly, HDR-BT offers good toxicity profiles. Radiation proctitis demands careful management. Keywords: Docal Dose Escalation, PSMA-PET, mpMRI Digital Poster 4354 Histopathological validation of PSMA-PET-based prediction of the ISUP grading of individual prostate cancer lesions Philipp M. A. Waibel 1 , Ievgen Glavynskyi 2 , Tobias Fechter 3 , Michael Mix 4 , Sophia L. Bürkle 1 , Felix Kind 4 , August Sigle 5 , Cordula A. Jilg 5 , Christian Gratzke 5 , Oliver Schilling 2 , Martin Werner 2 , Martin T. Freitag 4 , Peter Bronsert 2 , Constantinos Zamboglou 1,6 , Simon K. B. Spohn 1 , Anca-Ligia Grosu 1 1 Radiation Oncology, University Medical Center and DKTK Partner Site Freiburg, Freiburg, Germany. 2 Institute of Surgical Pathology, University Medical Center and DKTK Partner Site Freiburg, Freiburg, Germany. 3 Radiation Oncology - Division of Medical Physics, University Medical Center and DKTK Partner Site Freiburg, Freiburg, Germany. 4 Nuclear Medicine, University Medical Center and DKTK Partner Site Freiburg, Freiburg, Germany. 5 Urology, University Medical Center and DKTK Partner Site Freiburg, Freiburg, Germany. 6 German Oncology Center, European University of Cyprus, Limassol, Cyprus Purpose/Objective: Radiomic Features (RFs) ofPSMA-PET hold great potential for individual non-invasive risk stratification of prostate cancer (PCa). This study evaluatedthe
optimal threshold values of these RFs to identify PCa volumes in ISUP GG 3&4. Results:
Due to incomplete histopathological sections in two patients and an excessively long interval between PET- CT and resection in one patient,thirty-two patientswere included in the final analysis. The median ISUP GG of the PCalesions was 3 (range 1 – 4). Mean and maximum SUV (SUVmean and SUVmax) of the PCa lesions correlated significantly to ISUP GG(p = 0.0008, p = 0.004)with a more distinct correlation for cohort I compared to cohort II. QSZHGE correlated similarly to ISUP GG (p = 0.02). ROC analysis to detect ISUP GG 3&4 for cohort I yielded highly significant thresholds of 4.0 g/ml and 7.2 g/ml (sensitivity/specifity 1.00/0.64 and0.85/0.71) for SUVmeanand SUVmax, respectively. Conclusion: PSMA-PET is able to identify the ISUP GG of individual PCa lesions. These findings underscore the relevance of PSMA-PET/CT in planning focal dose escalation in radiotherapy. References: 1.Zamboglou C, Carles M, Fechter T, Kiefer S, Reichel K, Fassbender TF, u. a. Radiomicfeaturesfrom PSMA PET for non- invasive intraprostatictumordiscrimination and charac terization in patientswith intermediate- and high- riskprostatecancer - a comparisonstudywithhistologyreference. Theranosti cs. 13. April 2019;9(9):2595–605 Keywords: Prostate Cancer; Gleason Score, Imaging
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