ESTRO 38 Abstract book

S851 ESTRO 38

Gy in 4 fractions, twice a day, had the same effectiveness and tolerability of a total dose of 15 Gy in 5 daily fractions. However, the 2-days treatment was more comfortable and time-saving for patients (pts), in a variety of metastatic malignancies, with the exception of prostate cancer. In fact, in metastatic prostate disease, better outcome and lower toxicity were observed with a longer therapeutic schedule. Aim of our study was to evaluate the possibility to deliver the higher dose (15 Gy) in 4 fractions twice a day, in the specific setting of HBI defined as middle half body (MHB: pelvis, femurs and lumbar spine) by using a multiple field 3D-conformal technique to reduce toxicity. Material and Methods A phase I trial in 3-dose escalation steps was designed: 13 Gy (3.25 Gy-fractions), 14 Gy (3.5 Gy-fractions), and 15 Gy (3.75 Gy-fractions). The eligibility criteria included prostate cancer with painful bone metastatic disease in MHB fields, ECOG performance status ≤ 3, life expectancy > 3 months, no severe bone marrow dysfunction. Treatment was delivered in 2 days with twice-daily fractionation and at least 6 hours interval. Pts were treated in cohorts of 6-12 to define the maximum tolerated dose (MTD). The dose-limiting toxicity (DLT) was defined as any acute toxicity of grade 3 or greater, using the RTOG scale. Pain was recorded using a visual analogue scale. IAEA pain and drug score were also registered. Results 25 patients were enrolled. Only grade 1-2 acute toxicity was recorded. No pts experienced DLT. With a median follow-up of 7.4 months, only two case of G1 skin late toxicity were observed. The overall (complete plus partial) response rate for pain was 84% (21/25 pts): 9 pts had complete pain relief (VAS=0), 10 pts showed at least 30% VAS reduction, 2 pts showed an improvement in pain score and drug score with 20 and 25% VAS reduction respectively. Conclusion The MTD of short course MHB radiotherapy in patients with bone metastases is 15 Gy. Preliminary data on palliative efficacy are promising. EP-1577 Prostate SBRT with Gantry-based LINAC without ConeBeam. Toxicity outomes of 205 patients P. Castro Peña 1 , A. Henao 1 , P. Murina 1 , O. Muriano 1 , L. Suarez Villasmil 1 , A. Giraudo 1 , J.C. Archilla 1 , D. Venencia 1 , S. Zunino 1 1 Instituto Zunino - Fundacion Marie Curie, Radiation Oncology, Cordoba, Argentina Purpose or Objective To describe the technique of SBRT in 5 fractions, with IGRT ExacTrac only based, in patients with prostate cancer. Analyze of toxicity and biochemical response, in patients with ace of 6 months of follow-up Material and Methods Between Nov / 13 and Jun / 15, 223 patients with a positive prostate cancer biopsy were treated; Mean initial PSA = 25 ng / ml [0.42-1890] and mean prostate volume = 52.8 g [18.1-134]. All were irradiated with SBRT technique in 5 fractions (alternate days), following the institutional protocol. For IGRT (intra and interfraction) based on ExacTrac, 4 intraprostatic fiducial markers were implanted 2 weeks before. Virtual simulation based on CT with 1mm cuts at the prostate level. Drawing of volumes and dosimetry with planning system iPLAN-Net (BrainLAb) and Eclipse (Varian). Prescribed dose in 95% PTV-prostate = 40 Gy (95.6%) and 36.25 Gy (4.4%), according to institutional medical criteria. The patients were irradiated with Novalis Tx technology (BrainLab-Varian), high resolution multilamellar collimator (HDMLC) with 2.5mm plates. They were planned and irradiated with IMRT-dynamics technique, using 9 beams of 6 MV. Genitourinary toxicity (GU) was evaluated using the IPSS (International Prostate Symptom Score) (0-35 points) and

in selected PC oligometastatic pts with bone metastases (BM) to improve local control and delay the start of ADT or pharmacologic second-line therapy. Material and Methods Between October 2010 and July 2018, in 17 oligometastatic PC pts with a total of 20 BM local control (LC) rate, biochemical progression free-survival (b-PFS) and time to beginning of ADT were evaluated.Median age was 72 years (range, 57-87), median Gleason score at the primary diagnosis was 7 (range, 5-9). Median time from primary treatment to SBRT was 53 months (range 2–134 months). Diagnosis of BM was documented by Choline- PET/CT. Median PSA value before SBRT was 2.25 ng/ml (range, 0-46.8). Ten (59%) oligometastatic ADT-free pts underwent SBRT alone, while the other 7 (41%) oligometastatic castration-resistant prostate cancer (CR- PC) pts, continued ADT. Three (18%) pts underwent SBRT for two synchronous BM. The BM sites were: pelvis in 12 (60%), spine and ribs in 6 (30%), and in 2 (10%) cases, respectively. Gross tumor volume (GTV) was delineated using Choline-uptake and planning target volume was defined as the GTV plus a 5 mm isotropic margin. Radiotherapy schedules adopted were 5 × 5-8Gy in 13 (65%) BM and 3 × 9-10Gy in 7 (35%) BM. Response was assessed with PSA evaluation every 3 months during the first year and then every 6 months. Pts with a reduction or a stability of PSA level were considered responders, Choline-PET-CT was done in case of an increase of PSA level. Results The median follow-up was10 months (range 3-96). All (100%) patients had a decrease of PSA level after SBRT. Nine (53%) pts remained b-PFS, while8/17(47%) pts had new PSA increase after a median time of 8 months (2-48). Among biochemical progression pts, Choline-PET/TC showed LC in 100% of the treated lesions and a disease progression in other sites.At last follow-up one (6%) patient has died for PC, the other 16 (94%) were alive. Of note, 7 CR-PC pts before SBRT continued ADT but they did not have to start second-line therapy; 2/10 (20%) ADT-free pts before SBRT had to start ADT due to disease progression for an ADT-free survival of 9 months (3-96). No SBRT related acute or late toxicities were observed. Conclusion Our experience showed that SBRT of BM was highly effective with an excellent risk-benefit profile. SBRT in PC bone oligometastases pts should be evaluated to improve response rate and delay ADT or pharmacologic second-line therapy. EP-1576 Middle Half Body Radiotherapy in bone metastases from prostate cancer: a phase I study A. Zamagni 1 , M. Buwenge 1 , G. Siepe 1 , A. Arcelli 1 , C.M. Donati 1 , S. Bisello 1 , G. Macchia 2 , F. Deodato 2 , S. Cilla 3 , M. Ferro 2 , V. Picardi 2 , M. Boccardi 2 , E. Arena 2 , A. Ianiro 2 , P. Farina 4 , C. Pozzo 4 , A.A. Woldemariam 5 , T. Wondemagegnhu 5 , G.P. Frezza 6 , A.G. Morganti 1 , S. Cammelli 1 1 Radiation Oncology Center- Department of Experimental- Diagnostic and Specialty Medicine – DIMES, University of Bologna- Sant'Orsola-Malpighi Hospital, Bologna, Italy ; 2 Radiotherapy Unit, Fondazione di Ricerca e Cura "Giovanni Paolo II", Campobasso, Italy ; 3 Medical Physics Unit, Fondazione di Ricerca e Cura "Giovanni Paolo II", Campobasso, Italy ; 4 Medical Oncology Unit, Fondazione di Ricerca e Cura "Giovanni Paolo II", Campobasso, Italy ; 5 Department of Radiotherapy, Black Lion Hospital, Addis-Ababa, Ethiopia ; 6 Radiation Oncology Unit, Bellaria Hospital, Bologna, Italy Purpose or Objective In 2001 a clinical randomized trial from IAEA tested 2D Half Body Irradiation (HBI) for palliative treatment of multiple bone metastases demonstrating that a dose of 12