ESTRO 2020 Abstract book

S654 ESTRO 2020

anatomopathological results were: 22 (38,6%) pT3a, 12 (21,1%) pT3b, 6 (10,5%) pN1 and 10 (17,5%) pNx, 6 (10,5%) Gleason Score (GS) <6, 33 (58%) GS = 7 and 16 (28%) GS > 8; 22 (38,6%) R0 and 34 (59,6%) R1, 43 (75,4%) positive perineural invasion (PNI) and 13 (22,8%) positive lympovascular invasion (LVI). Postoperative PSA was 0.61 (range, 0.01-17.66). In 54 patients, imaging test showed 44 (77.2%) local failure (LF), 2 (3.5%) local and lymphatic node failure, 5 (8.8%) lymphatic node failure, and 2 (3.5%) distance disease. PTV included was: 28 (49.1%) tumor bed alone, 20 (50.9%) tumor bed and pelvic nodes, and 6 of them received treatment about metastasis (4 lymphatic and 2 bones metastasis). RT treatment was done through VMAT-daily IGRT system with a total dose of 74Gy/37 fractions. Toxicity was evaluated with CTC-AE v4. Statistical analysis was performed with SPSS 22.0 software package (IBM SPSS, Inc., Chicago, IL, USA). Results With a mean follow up of 31.2 months, 18 (31.6%) patients had biochemical failure after RT treatment. FBFS (Free Biochemical Failure Survival) was 67.9% and mean survival 43 months. Most important prognostic factor for BF was PSA preRT <0.5 ng/ml vs >0.51 ng/ml, 23.7% vs 57.1% respectively (p= 0.027). FBFS was 76.3% in PSA preRT <0.5 group and 42.9% in PSA preRT >0.51 group and mean FBFS 49.76 months (IC95% 41.3-58.2) in PSA preRT <0.5 and 28.9 months (IC95% 6.57-16.12) in PSA preRT >0.51, p = 0.021 (Log Rank) (Figure 1) . There are no other significant prognostic factors for BF. No patient had LF but there was 5 (8.8%) with lymphatic nodes failure, 7 (12.3%) with distance disease and 6 (10.5%) with oligorrecurrence. 1.8% of treated patients had genitourinary (GU) acute toxicity G3 and 26.3% was G1-2. GU chronic toxicity G1-2 was 15.8% and 3.5% G3. There was only gastrointestinal acute toxicity G1 3.5% and no chronic toxicity. Disease free survival (DFS) was in PSA preRT <0.5 68.4% and 64.3% in PSA preRT >0.51 and mean DFS 35.85 months (IC95% 29.71-42) in PSA preRT <0.5 and 42.71 months (IC95% 30.18-55.25) in PSA preRT >0.51.

Paolo II, UO di Fisica Sanitaria, Campobasso, Italy ; 3 Dipartimento di Medicina Specialistica Diagnostica e Sperimentale- DIMES- Azienda Ospedaliera-Universitaria S.Orsola-Malpighi, UO di Radioterapia, Bologna, Italy ; 4 PO ‘Veneziale’, UO di Oncologia Medica, Isernia, Italy ; 5 PO ‘Cardarelli, UO di Urologia, Campobasso, Italy ; 6 Università Cattolica S. Cuore- Fondazione Giovanni Paolo II, UO di Radiologia, Campobasso, Italy ; 7 Fondazione Policlinico Universitario A. Gemelli- IRCCS, UOC di Radioterapia- Dipartimento di Scienze Radiologiche- Radioterapiche ed Ematologiche, Roma, Italy Purpose or Objective To determine the efficacy and safety of stereobody radiosurgery (SRS) in the treatment of isolated bone metastases (mts) in prostate cancer (PC) patients (pts). Material and Methods Data from PC patients with <3 bone mts undergone single fraction stereotactic radiosurgery (SRS-DESTROY-2 phase I clinical trial) as exclusive treatment, or boost (SRS- vertebra phase I clinical trial) after conformal external beam radiotherapy (3D-CRT), were collected and analyzed. From October 2010 to December 2018, as per trials design, PC pts received SRS according to skeletal site (vertebral versus other bone lesions). In particular, vertebral mts received a 3D-CRT dose of 25 Gy in 10 fractions followed by a SRS dose of 8 Gy, 10 Gy, or 12 Gy, in subsequent escalated cohorts; other bone lesions were treated by subsequent escalated SRS doses ranging from 12 Gy to 24 Gy. Best radiologic response to SRS was evaluated by computed tomography (CT) scan, Magnetic Resonance (MR) or positron tomography (PET) scan, and classified according to the RECIST or PERCIST criteria. Objective response rate included complete response (CR) and partial response. Actuarial local control (LC) was defined as the time interval between the date of SRS and the date of inside SRS field relapse/progression of disease or the last follow-up visit. Toxicity was evaluated by CTC-AE scale. Results Forty-six pts carrying a total of 68 bone mts were selected for the enrolment. The median age was 73 years (range: 56-86), and the majority of patients (96%) presented Eastern Cooperative Oncology Group performance status 0-1. The most frequent anatomical districts were the pelvis (40%) followed by vertebral mts (35%), and a miscellanea of other sites, mainly ribs, sternum and scapula (17,25%). Overall, dose prescription to the Planning Target Volume ranged from 12 to 37 Gy (median dose: 24 Gy) and all lesions were treated with a volumetric arc radiotherapy technique. With a median follow-up of 18 months (1-66) no severe (> grade 3) acute or late toxicities were recorded, with only 3 pts reporting G2 toxicity (2 esophagitis and 1 ematological). The overall objective response rate was 75.0% (CI 95%:60.1-84.8) with a CR rate of 62%. The 2-years actuarial LC was 94% (median not reached). Conclusion This study confirms the activity and safety of SRS in the treatment of bone metastases in oligometastatic PC pts. Optimal SRS schedules should be defined taking into account the need to guarantee the best personalized radiation dose. PO-1154 Assessing the potential gains of a decision support system for primary treatment of prostate cancer Y. Van Wijk 1 , B. Ramaekers 2 , C. Oberije 3 , J. Van Roermund 4 , B. Vanneste 5 , P. Lambin 3 1 Maastricht university, School for Oncology and Developmental Biology, Maastricht, The Netherlands ; 2 Maastricht university medical centre+, Clincial Epidemiology and Medical Technology Assessment, Maastricht, The Netherlands ; 3 Maastricht University,

Conclusion High-dose RT with IGRT in postoperative prostate cancer patients is a safe and effective treatment for local control of tumor bed with an excellent acute and chronic toxicity results. PO-1153 Isolated bone metastases in prostate patients: preliminary analysis from two phase I trials on SRS F. Deodato 1 , A. Re 1 , A. Ianiro 2 , M. Boccardi 1 , M. Ferro 1 , S. Cammelli 3 , C. Romano 2 , V. Picardi 1 , D. Traficante 4 , A. Di Lallo 5 , M. Buwenge 3 , M. Ciuffreda 6 , M. Ferro 1 , S. Cilla 2 , V. Valentini 7 , A.G. Morganti 3 , G. Macchia 1 1 Università Cattolica S. Cuore- Fondazione Giovanni Paolo II, UO di Radioterapia, Campobasso, Italy ; 2 Università Cattolica S. Cuore- Fondazione Giovanni