ESTRO 36 Abstract Book

S706 ESTRO 36 2017 _______________________________________________________________________________________________

Our experience with VMAT-based SBRT in low-and intermediate–risk prostate cancer demonstrates favorable efficacy in tumor control and toxicity profile with no decrease in QOL as determined by I-PSS, IIEF. The general good quality of the clinical outcome and the results concerning GI and GU toxicities seem to confirm the robustness of the dosimetric paradigm adopted. Longer follow-up is needed to investigate complete safety and efficacy of the stereotactic treatments. EP-1330 Predictive factors for urinary toxicity in patients treated with radical ebrt for prostate cancer C. Pisani 1 , A. Galla 1 , D. Beldì 1 , G. Apicella 1 , G. Loi 2 , M. Krengli 1 1 University Hospital Maggiore della Carità, Radiotherapy, Novara, Italy 2 University Hospital Maggiore della Carità, Medical Physics, Novara, Italy Purpose or Objective Acute and late toxicity scores in patients treated with radical external beam radiotherapy (EBRT) for prostate cancer were correlated with dosimetry and clinical data in order to identify some predictors for urinary (GU) toxicity. Material and Methods This study enrolled 280 patients (pts) treated with EBRT as primary treatment for prostate cancer in our University Hospital. All patients had at least 24 months follow-up, with a median of 47 months (range: 40-98). According with NCCN risk classification, 18% of pts were at low risk, while the others were at intermediate or high risk. Prescribed dose was 74-78 Gy. Adjuvant androgen deprivation consisting of a luteinizing hormone-releasing hormone analog, was administered in 192 patients (68.6%). All patients completed a pre-EBRT questionnaire, registering baseline GU symptoms and patients’ medical history (diabetes,hypertension, previous surgery, and smoking) and were assessed by International Prostatic Symptom Score (IPSS). Toxicity was registered following a grading system based on the Radiation Therapy Oncology Group (RTOG). Acute toxicity was defined as toxicity occurring during or within 3 months after the end of EBRT. Late toxicity was defined as toxicity occurring for the first time >3 months after the end of EBRT or as acute toxicity lasting longer than 3 months. Acute and late GU toxicities were correlated with dosimetry and clinical parameters (age , presence of co-morbidities including previous TURP, tumor stage, initial PSA and Gleason Score). Results Median age was 74 years (range: 64-83); performance status according with Karnofsky scale was 90 (80-100). Fifty percent of pts had cardiovascular disease and 13% of them had undergone TURP before EBRT. Thirty-two percent of pts were treated with IMRT and 20% with IGRT. Median bladder volume at simulation was 263 cc. Thirty- one percent of pts experienced acute G1 GU toxicity, 24% G2 and 3% G3. No G4 GU acute toxicity was reported. Fourteen percent of pts experienced G1 late toxicity and 3% G2. We did not report any G3 or G4 GU toxicity. IPSS baseline value significantly correlated with acute GU toxicity in univariate (p=0.009) and multivariate (p=0.0002) analysis. The presence of nicturia (p=0.002), bladder urgency (p=0.024) and incontinence (p=0.024) also significantly correlated with GU toxicity. Bladder volume <200 cc at CT-simulation was also associated with toxicity (p=0.014), while maximum dose to bladder was correlated with late toxicity (p=0.014). The use of 3D-EBRT was significantly associated both with increased acute (p=0.032) and late (p=0.03) toxicity. Conclusion In our study pretreatment IPSS, nicturia, urgency and urinary incontinence at diagnosis, bladder volume < 200 cc during CT-simulation, the use of 3D-EBRT and maximum

dose to the bladder was predictive for specific moderate– severe acute urinary symptoms. EP-1331 Efficacy and safety of re-irradiation of locally recurrent prostate cancer with FFF-VMAT G.R. D'Agostino 1 , C. Franzese 1 , L. Di Brina 1 , S. Tomatis 1 , C. Iftode 1 , D. Franceschini 1 , E. Clerici 1 , G. Reggiori 1 , A. Tozzi 1 , P. Navarria 1 , M. Scorsetti 1 1 Istituto Clinico Humanitas, Radiotherapy and Radiosurgery, Rozzano Milan, Italy Purpose or Objective Despite considerable advances in technologies, especially with the introduction of IMRT, IGRT, and VMAT, re- treatment of locally recurrent prostate cancer with external beams radiation therapy remains controversial because of fear of major complications or unbearable side effects. In this study we report our experience on re- irradiation in a sample of 17 patients previously irradiated for prostate cancer. Material and Methods Patients affected by prostate cancer and previously submitted to radiotherapy were included in this study, provided that they had an increased PSA, diagnostic for biochemical relapse, and a PET-Choline revealing the presence of a local recurrence of disease. Re-irradiation consisted of a stereotactic treatment delivered by FFF IGRT-VMAT technology in 5 daily fractions. Clinical response was evaluated with PSA and physical examination. Toxicity assessment according to CTCAE (v. 4.01) criteria. During follow-up, PET-Choline was performed in the cases of PSA rising. Results Between November, 2012 and May, 2016, 17 patients (median age 78 years, range 59-82) were submitted to re-irradiation on prostate (n=10, 58.8%), prostatic bed (n=5, 29.4%) or prostate and local recurrence (n=2 seminal vesicle, ischium 11.8%). Previous treatment consisted on a median total dose of 74 Gy on prostate or prostatic bed (range 66-76). Ten patients had also received radiotherapy on seminal vesicles, four patients on pelvic lymph-nodes. Median time from previous radiotherapy was 80 months (range 26-116). Median PSA at the moment of recurrence was 3.1 ng/ml (average 4, range 1.2-13.5). As a re-irradiation, a median total dose of 25 Gy (range 25-30) was delivered in a median number of 5 fractions (range 5-6). An immediate biochemical response was observed in all cases. Median PSA nadir after treatment was 0.77ng/ml (average 1.33, range 0.19-6.0, p=0.0004)) The sole acute toxicity reported was genito-urinary, mainly represented by pollakiuria and dysuria grad e 1 (n=9, 52.9%) or grade 2 (n=2, 11.8%). One patient (5.9%) had a grade 3 hematuria, was hospitalized and submitted to continuous bladder irrigation. A late grade 1 GU toxicity was observed in 3 patients (17.7%). No other toxicities were observed. At a median follow-up of 16 months (range 6-36, calculated from the time of recurrence diagnosis) 8 patients (47.1%), experienced a biochemical recurrence, confirmed by a positive PET-choline in 5 cases (29.4%). Median BFS was 19 months, 1- and 2-year BFS was 84.6% and 32.2%, respectively. Median LC was 24 months, 1- and 2-year LC was 90.9% and 40.4%, respectively. All patients are still alive, 5 of them with measurable disease. Median OS was 96 months from the initial diagnosis (range 59-151). Conclusion With the technological novelties offered by modern radiotherapy, re-irradiation of patients affected by prostate cancer, and previously treated with radiation therapy, confirms its safety and efficacy. Therefore, it can be considered a valuable option for local recurrence of this disease. EP-1332 Contouring variability with CT and MRI of prostate cancer for radiation planning