ESTRO 2023 - Abstract Book

S153

Saturday 13 May

ESTRO 2023

Purpose or Objective Radiotherapy is a commonly used treatment method for patients with high-risk prostate cancer. Emerging evidence shows a benefit of increasing the dose to the dominant intra-prostatic lesion. In this study we examined the performance of [68Ga]PSMA-11 PET (PSMA-PET), [11C]Acetate PET/CT (ACE-PET) and multiparametric MRI (mpMRI) for the detection of intra-prostatic lesions in patients with intermediate and high-risk prostate cancer, using whole-mount histopathology as the reference standard, stratified by Gleason score (GS) and lesion volume. Materials and Methods Fifthy-five study participants with intermediate to high-risk prostate cancer planned for radical prostatectomy were included. PSMA-PET/mpMRI and ACE-PET/CT examinations were performed prior to surgery. After excision, the specimen was placed in a custom-made mold to prevent deformation and an ex-vivo T2w MRI was performed. The specimen was fixed in formalin at least 24 h prior to slicing into 5 mm thick slices from apex to base. Standard histopathology procedures including paraffin embedding and microtoming in 5 µ m thick slices were performed. Each slice was stained with hematoxylin and eosin and examined by the pathologist, who segmented and graded tumor foci. The slices were registered to the in- vivo images using the software MICE toolkit, resulting in an uncertainty of below 2 mm. Two radiologists examined the mpMRI data and two nuclear medicine specialists examined the PET data in a blinded manner and reported the findings according to PI-RADS v2.1 and E-PSMA guidelines, respectively. The detection rate was determined and stratified by GS and lesion volume. Results The histopathological evaluation found 130 lesions >0.05 cc, 88 lesions >0.1 cc and 43 lesions >0.5 cc. The GS-distribution was 26% (3+3), 38% (3+4), 18% (4+3), 15% (4+4) and 3% (>4+4). The mean detection rate for lesions with a GS ≥ 3+4 and a volume >0.05 cc (96 in total) was 18% (ACE-PET), 40% (mpMRI) and 42% (PSMA-PET). 56 (58%) lesions in this group were identified by either mpMRI, PSMA or both. The histopathological examination identified 42 lesions with a GS ≥ 3+4 and a volume >0.5 cc. The mean detection rate for this group were 37% (ACE-PET), 70% (PSMA-PET) and 74% (mpMRI). 40 (93%) lesions in this group were identified by either mpMRI, PSMA or both. Conclusion The degree of detection increases with increasing GS and lesion volume. PSMA-PET and mpMRI generate high detectability, but they do not always detect the same lesions, which may indicate the value of a combined PSMA-PET/MRI examination. MO-0220 Two-year impact of bowel symptoms on HRQoL after RT for prostate cancer with pelvic node irradiation M. Pavarini 1 , L. Rago 2 , F. Munoz 3 , A. Magli 4 , D. Cante 5 , G. Girelli 6 , A. Bresolin 1 , B. Noris Chiorda 7 , J.M. Waskiewicz 8 , B. Avuzzi 7 , E. Garibaldi 9 , A. Faiella 10 , E. Villa 11 , P. Ferrari 12 , L. Ferella 3 , C. Piva 5 , T. Statuto 13 , M. Gatti 14 , T. Rancati 15 , R. Valdagni 7 , V.L. Vavassori 11 , G. Sanguineti 16 , N.G. Di Muzio 17 , C. Fiorino 1 , C. Cozzarini 17 1 IRCCS San Raffaele Scientific Institute, Medical Physics, Milano, Italy; 2 Ospedale San Carlo, Radiotherapy, Potenza, Italy; 3 Ospedale Regionale Parini-AUSL Valle d’Aosta, Radiotherapy, Aosta, Italy; 4 Azienda Ospedaliero Universitaria S. Maria della Misericordia, Radiotherapy, Udine, Italy; 5 Ospedale di Ivrea, Radiotherapy, Ivrea, Italy; 6 Ospedale degli Infermi, Radiotherapy, Biella, Italy; 7 Fondazione IRCCS Istituto Nazionale dei Tumori, Radiotherapy, Milano, Italy; 8 Comprensorio Sanitario di Bolzano, Radiotherapy, Bolzano, Italy; 9 A.O. SS. Antonio e Biagio, Radiotherapy, Alessandria, Italy; 10 Istituto Nazionale dei Tumori "Regina Elena", Radiotherapy, Roma, Italy; 11 Cliniche Gavazzeni-Humanitas, Radiotherapy, Bergamo, Italy; 12 Comprensorio Sanitario di Bolzano, Medical Physics, Bolzano, Italy; 13 Ospedale San Carlo, Biology, Potenza, Italy; 14 Istituto di Candiolo - Fondazione del Piemonte per l'Oncologia IRCCS, Radiotherapy, Candiolo, Italy; 15 Fondazione IRCCS Istituto Nazionale dei Tumori, Prostate Cancer Program, Milano, Italy; 16 Istituto Nazionale dei Tumori "Regina Elena", Radiotherapy, Rome, Italy; 17 IRCCS San Raffaele Scientific Institute, Radiotherapy, Milano, Italy Purpose or Objective To prospectively assess the impact of patient-reported intestinal toxicity (IT) on 2-year health-related quality of life (HRQoL) in a large multi-institute cohort of patients (pts) who underwent radiotherapy (RT) including pelvic nodal irradiation (PNI) for prostate cancer (PCa) with different intent. Materials and Methods A prospective multi-Institute study aimed at evaluating IT after RT including PNI along with its detrimental impact on pts’ HRQoL recruited 886 between 2011 and 2021. The Inflammatory Bowel Disease Questionnaire (IBDQ) was administered at baseline, at RT mid-point and end, at 3 and 6 months and thereafter every 6 months up to 5 years. IBDQ items analyze four Domains, that of Bowel symptoms (BOWEL) and their impact on Emotional (EMOT), Social (SOCIAL) and Systemic (SYST) aspects of HRQoL. The 554 pts considered for the current analysis had complete baseline, 2-years and both RT mid-point and end RT (90%) questionnaires or at least one between RT mid-point and end (10%). The differences between baseline and 2-year single Bowel items (n=10) and Domain scores were investigated, accounting for the BOWEL baseline and Worst (defined as the largest BOWEL worsening between baseline and RT mid-point or end). Monotonic relationships between 2-year variations of single BOWEL items and EMOT, SOCIAL and SYST were also investigated to quantitatively assess the 2-year bowel symptoms mostly related to HRQoL worsening, through the Spearman’s rho coefficient. Results The distributions of the differences between each IBDQ Domain score at baseline and at 2 years were tested via the Wilcoxon signed-rank test. Differences were found to be significant for three out of four Domains: EMOT completely recovered within 2 years from RT end (p=0.42), while the others did not (p<0.001). BOWEL baseline values did not impact the deterioration of BOWEL and SYST; on the contrary, baseline values below and above the first quartile (Q1) resulted in stable impaired SOCIAL scores, respectively. Instead, patients with lower Worst values (Q1 did not show significant worsening: this result suggests that the intensity of acute bowel symptoms is associated to a degradation of the 2-year SOCIAL domain. Spearman's rho coefficients suggest that the bowel symptoms related to “Urge to Go to Bathroom” (IBDQ24, ρ = 0.31-0.39), “Accidental Soiling” (IBDQ26, ρ = 0.28-0.37), “Gas Passage” (IBDQ17, ρ = 0.24-0.34) and “Abdominal Bloating” (IBDQ20, ρ = 0.26-0.34) were the ones more associated to individual deterioration of EMOT, SOCIAL and SYST.