ESTRO 38 Abstract book

S439 ESTRO 38

Petrucci 15 , P. Salmoiraghi 16 , E. Villa 17 , J.M. Waskiewicz 18 , N.G. Di Muzio 5 , T. Rancati 6 , C. Fiorino 19 , C. Cozzarini 5 1 Istituto di Candiolo-Fondazione del piemonte per l'Oncologia IRCCS, Radiotherapy, Candiolo TO, Italy ; 2 Ospedale Regionale U Parini - AUSL Valle d'Aosta, Radiotherapy, Aosta, Italy ; 3 Ospedale di Ivrea- ASL TO4, Radiotherapy, Ivrea, Italy ; 4 Fondazione IRCCS Istituto Nazionale Tumori, Radiotherapy, Milano, Italy ; 5 San Raffaele Scientific Institute, Radiotherapy, Milano, Italy ; 6 Fondazione IRCCS Istituto Nazionale Tumori, Programma prostata, Milano, Italy ; 7 Ospedale degli infermi, Medical Physics, Biella, Italy ; 8 Comprensorio Sanitario di Bolzano, Medical Physics, Bolzano, Italy ; 9 Fondazione IRCCS Istituto Nazionale Tumori, Medical Physics, Milano, Italy ; 10 Ospedale degli infermi, Radiotherapy, Biella, Italy ; 11 Istituto Nazionale dei Tumori Regina Elena, Medical Physics, Roma, Italy ; 12 Ospedale di Udine, Radiotherapy, Udine, Italy ; 13 Istituto di Candiolo-Fondazione del piemonte per l'Oncologia IRCCS, Medical Physics, Candiolo TO, Italy ; 14 Ospedale di Udine, Medical Physics, Udine, Italy ; 15 Ospedale di Ivrea- ASL TO4, Medical Physics, Ivrea, Italy ; 16 Cliniche Gavazzeni Humanitas, Medical Physics, Bergamo, Italy ; 17 Cliniche Gavazzeni Humanitas, Radiotherapy, Bergamo, Italy ; 18 Comprensorio Sanitario di Bolzano, Radiotherapy, Bolzano, Italy ; 19 Fondazione Centro San Raffaele, Department of Medical Physics, Milano, Italy Purpose or Objective Assessing predictors of patient-reported incontinence (INC) 1-year after post-prostatectomy IMRT, focusing on the impact of dose. Material and Methods 390 patients (pts) treated during 2012-2018 with adjuvant (ADV) or salvage (SALV) intent were enrolled in a registered (ClinicalTrials.gov) multi-centric cohort study aimed to assess predictors of intestinal, haematological and urinary toxicity. IMRT was delivered with conventional (n=228, 66-77.4Gy) or moderate hypo-fractionation (n=162, 65-75Gy, 2.2-2.7Gy/fr). Clinical and dosimetry data were prospectively collected including ICIQ-SF questionnaire for INC evaluation at baseline, half-RT, end- RT and every 6 months up to 5 years after IMRT. At the time of analysis, mature 1-year data were available; four ICIQ-based end-points were considered: a) “subjective” severe INC: ICIQ-SF>12; b) “subjective” moderate INC: ICIQ-SF>5; c) daily leakage: ICIQ3 (i.e: the score of question 3)>2; d) objective moderate INC: ICIQ3+4 (i.e: the sum of the scores of questions 3 and 4) >4. Predictors of 1-year prevalence were assessed through uni- (UVA) and multi-variable (MVA) logistic regression: potential clinical predictors included age, time from surgery, intent (ADV vs SALV), comorbidities and patient habits, type of surgery and baseline INC. The prescribed EQD2 (i.e.: PTV D mean ) was also considered by applying alpha-beta values equal to 5 and 1Gy (EQD2_5/EQD2_1), reported in literature for late urinary toxicity. UVA/MVA were repeated excluding pts with the investigated symptoms at baseline. Results In total, 356/390 pts filled in baseline ICIQ-SF and 238/356 pts the 1-year ICIQ-SF. Pts experiencing a, b, c, d were 44 (18%), 131 (55%), 124 (52%) and 124 (52%) respectively. The corresponding baseline values were 33 (14%), 114 (48%), 102 (43%) and 103 (43%). For all end-points, baseline ICIQ-SF was the strongest predictor (p<0.0001, OR: 1.30-1.33), even excluding pts with baseline symptoms (p<0.0001, OR: 1.25-1.37). When excluding pts with symptoms at baseline, EQD2_1 was predictive of both objective end-points c and d (p=0.02, OR: 1.089-1.090). At MVA, ICIQ-SF and EQD2_1 were independent predictors: the resulting two-variable models well fit data (H&L test: 0.60-0.70) with good calibration (slope= 0.96, R 2 =0.93). The 1-year risk of daily leakage (n=132 patients, 42 daily leakage: 32%) is plotted in the figure against EQD_1 for

had clinical stage T2a or less and 1,309 (56.5%) had Gleason score (GS) less than 7. 542 patients (23.4%) received supplemental EBRT and 1,137 (49.1%) received hormonal treatment (HT). Median follow-up period was 60.0 months (interquartile range, 58.7–60.9 months). The 5-year bFFF rate in all patients, 1028 low risk (LR) patients, 1114 intermediate risk (IR) patients and 133 high risk (HR) patients were 93.6%, 94.9%, 92.7% and 91.1%, respectively (Fig. 1). The 5-year bFFF rate in PI group and EBRT combination therapy group were 93.7% and 93.3%, respectively. On multivariate analysis, older age, GS and the percent volumes of the prostate receiving 100% of the prescribed dose (prostate V100) ( p = 0.0003, <0.0001 and 0.0107, respectively) in all patients, older age, PSA and prostate V100 ( p = 0.0002, 0.0048 and 0.0012, respectively) in LR patients, and GS and HT ( p = 0.0003 and 0.0077, respectively) in IR patients were significantly associated with bFFF. There were no significant predictors in HR patients (Table 1).

Conclusion PI with or without EBRT resulted in excellent short-term biochemical outcomes at all risks, especially in HR patients in Japan. Older age, PSA and prostate V100 in LR patients and GS and HT in IR patients independently affected bFFF. PO-0837 Dose-effect relationship for early late incontinence after IMRT in post-prostatectomy patients P. Gabriele 1 , F. Munoz 2 , D. Cante 3 , B. Avuzzi 4 , C. Bianconi 5 , F. Badenchini 6 , B. Farina 7 , P. Farina 8 , E. Garibaldi 1 , T. Giandini 9 , G. Girelli 10 , V. Landoni 11 , A. Magli 12 , A. Maggio 13 , E. Moretti 14 , B. Noris Chiorda 4 , E.