ESTRO 2020 Abstract book

S671 ESTRO 2020

findings with ROC analysis. Patients with distant metastasis and receiving hormonotherapy before 68 Ga- PSMA-PET/CT delivery were excluded. Results Median age was 68 years (45 – 75 years). Median pre- treatment PSA and SUV max of primary tumor were 17.6 ng/dL (2.3 – 301.0 ng/dL) and 12.8 (4.3 – 84.3), respectively. 234 patients (86%) were treated with definitive radiotherapy, and 37 patients (14%) were treated with radical prostatectomy. The clinical T stages were: 12 patients (4%) T2a, 97 patients (36%) T2b, 51 patients (19%) T2c, 39 patients (14%) T3a, and 72 patients (27%) T3b. 81 patients (30%) had regional lymph node metastasis. 139 patients (51%) had GS 7, 61 patients (23%) had GS 8, 61 patients (23%) had GS 9 and 10 patients (3%) had GS 10 disease. The area under curve (AUC) for PSA and SUV max of primary tumor regarding lymph node metastasis were 0.690 (95% CI 0.620 – 0.761) and 0.650 (95% CI 0.575 – 0.725), respectively. The cut-off values of PSA and SUV max for predicting lymph node metastasis were 21.2 ng/dL and 13.9, respectively. The AUC’s for RF, YF and PN for detecting 68 Ga-PSMA positive lymph node metastasis were 0.745 (95% CI 0.685 – 0.805), 0.731 (95% CI 0.668 – 0.794), and 0.704 (95% CI 0.642 – 0.766), respectively (Figure 1).

Gemelli - IRCCS- Università Cattolica del Sacro Cuore, Dipartimento di Scienze Radiologiche- Radioterapiche ed Ematologiche-UOC di Radioterapia Oncologica- Gemelli- ART, Rome, Italy ; 7 Fondazione "Giovanni Paolo II"- Università Cattolica del Sacro Cuore, UO di Fisica Sanitaria, Campobasso, Italy Purpose or Objective Several trials showed a benefit in prostate cancer survival outcomes with dose escalation, with a higher toxicity rate. Aim of this study was to show the results in terms of late toxicity and long term outcomes on a series of prostate cancer patients treated by an integrated boost to the dominant intraprostatic lesion (DIL). Material and Methods Inclusion criteria of the study were: histologically proven adenocarcinoma of the prostate; cT2/3N0M0 stage, based on abdominal and pelvic Magnetic Resonance Imaging and bone scan; Gleason Score < 8; nodal involvement risk less than 20% (calculated by Roach formula); age >18 years; Eastern Cooperative Oncology Group performance status ≤ 2. The trial was approved by the Institutional Ethics Committee. Patients were treated using Intensity Modulated Radiotherapy, with a simultaneous integrated boost to the DIL, defined on the staging MRI. Prostate and seminal vesicles prescribed dose was of 72 Gy/1.8 Gy per fraction; while DIL received 80 Gy / 2 Gy per fraction. Androgen deprivation therapy was administered according to guidelines. The primary endpoint was to evaluate acute toxicity, in order to reduce the rate of acute grade > 2 GI toxicity as already reported in the preliminary analysis. Secondary endpoints were late toxicity and biochemical disease-free survival. Kaplan-Meier product-limit method was used. RTOG scale was used to evaluate toxicity. Results Forty four patients were enrolled, with a median age of 73 (59-81). Median follow up was 66.5 months (25-144 months) . The 34.1% of patients were classified in the intermediate risk group, while the others in the high and very high risk group, according the current guidelines. Actuarial 5-year late GI toxicity free survival was: 76.6% of G1; 100% of G3. Actuarial 5-year late GU toxicity free survival was: 88.8% of G1; 97.6% of G3. Nobody experienced G4 toxicity. Biochemical Disease Free Survival was of 94.9% at 5 years, with all patients experimented local control. Five-year overall survival was of 94.6% and 96.9% the metastasis free survival. Conclusion The reported results, in term of toxicity and survival outcomes are encouraging in our sample. Further studies, even on-going or with the use of more accurate imaging methodologies could demonstrate the utility of a boost to DIL. PO-1186 Impact of a low FODMAP diet on rectal gas and rectal volume during radiotherapy of prostate cancer C. Schaefer 1 , C. Zamboglou 2 , N. Volegova-Neher 2 , C. Martini 2 , N.H. Nicolay 2 , N. Schmidt-Hegemann 1 , P. Rogowski 1 , M. Li 1 , C. Belka 1,3 , A. Grosu 2,4 , T. Brunner 5 1 Ludwig-Maximilians-Universität München- University Hospital, Department of Radiation Oncology, Munich, Germany ; 2 Albert-Ludwigs-Universität Freiburg- University Hospital, Department of Radiation Oncology, Freiburg, Germany ; 3 German Cancer Consortium DKTK, Partner Site Munich, Munich, Germany ; 4 German Cancer Consortium DKTK, Partner Site Freiburg, Freiburg, Germany ; 5 Otto-von-Guericke-Universität Magdeburg- University Hospital, Department of Radiation Oncology, Magdeburg, Germany Purpose or Objective Small inter- and intrafractional prostate motion was shown to be a prerequisite for precise radiotherapy (RT) of

Conclusion The clinical parameters may help to predict the risk of lymph node metastasis in prostate cancer patients. However RF is still a reliable tool to predict lymph node metastasis in prostate cancer patients. Because the conclusion of the present study is premature and 68 Ga- PSMA-PET/CT is not accepted as a routine imaging modality for PC staging, the long-term results of this study are required to interpret these findings in clinical practice. PO-1185 Results of prostate cancer patients treated by integrated boost to dominant intraprostatic lesion A.R. Alitto 1 , M. Buwenge 2 , G. Macchia 3 , M. Ntreta 2 , G. Siepe 2 , E. Galofaro 2 , F. Bertini 2 , M. Ferioli 2 , E. Mazzeo 4 , E. Ippolito 5 , G. Mantini 6 , M. Ferro 3 , A. Re 3 , S. Cilla 7 , V. Valentini 6 , F. Deodato 3 , A.G. Morganti 2 , S. Cammelli 2 1 Fondazione Policlinico Universitario A. Gemelli - IRCCS, Dipartimento di Scienze Radiologiche- Radioterapiche ed Ematologiche-UOC di Radioterapia Oncologica- Gemelli- ART, Rome, Italy ; 2 Azienda Ospedaliera-Universitaria S.Orsola-Malpighi, Dipartimento di Medicina Specialistica Diagnostica e Sperimentale-DIMES- U.O. di Radioterapia, Bologna, Italy ; 3 Fondazione "Giovanni Paolo II"- Università Cattolica del Sacro Cuore, UO di Radioterapia, Campobasso, Italy ; 4 Az. Ospedaliero Universitaria of Modena-Policlinico, U.O. di Radioterapia, Modena, Italy ; 5 Campus Bio-Medico Universitario, U.O. di Radioterapia, Roma, Italy ; 6 Fondazione Policlinico Universitario A.