Abstract Book

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free survival was lower in the high risk group compared to the low risk group and on breakdown of the intermediate and high risk group by number of risk factors, a lower biochemical relapse-free survival was evident with an increasing number of risk factors. Within each risk group, the estimates of risk for patients with two factors present were consistently lower than those with only one factor although these differences were not statistically significant, suggesting that classification by risk group is a much stronger correlate of outcome than the number of factors present. Conclusion This study reports on the outcomes of the largest prospectively recruited cohort of Australian prostate cancer patients treated with definitive radiotherapy, with a median follow-up of 92 months. Our results show that radiotherapy is an effective definitive treatment option for men with prostate cancer. EP-1574 Salvage nodal RT for PSMA avid oligomets in hormone naive prostate cancer patients: GCC Experience. T.S. Lim 1,2 , J. Dortmans 3 , S. Sia 1,2 , R. Chee 2,4 1 Fiona Stanley Hospital, Genesis Cancer Care, Perth, Australia 2 Perth Radiation Oncology, Genesis Cancer Care, Perth, Australia 3 Fiona Stanley Hospital, Department of Radiation Oncology, Perth, Australia 4 Shenton House, Genesis Cancer Care, Perth, Australia Purpose or Objective To report our results of salvage nodal radiotherapy (RT) for Ga-PSMA/Flourocholine PET avid recurrent oligometastases in hormone naive prostate cancer patients following their initial radical prostate treatment. Material and Methods From January 2014 to October 2017, forty-seven prostate cancer patients with PSA progression and 18F-choline PET or PSMA PET detected recurrent oligometastases were treated with salvage nodal +/- prostatic bed radiation therapy in the absence of any prior or concurrent hormonal manipulation. All patient were previously treated with radical prostatectomy for their localised prostate cancer. All patients received elective nodal RT with boost to the involved nodes +/- prostatic bed using VMAT techniques with the medianRT dose to elective nodes of 54 (52-56) Gy and to involved nodes of 66 (66- 70) Gy. and to prostatic bed of 66 (66-70)Gy. Results The median follow up was 15 (4-36) months. The median pre-salvage nodal RT prostate-specific antigen (PSA) was 1.1 (0.08-24.9) ng/ml. The median time from initial radical prostatectomy to PSA failure with PSMA/Flurocholine PET detected recurrent disease was 42.5 (1-164) months. Most patients (40/47) achieved PSA response immediately after salvage nodal RT with post- RT PSA lower than pre-RT PSA. Fourteen percent of patients achieved undetected PSA and 20% of patients were found to have PSA progression (with post-RT PSA greater than pre-RT PSA) during the last follow up. All patients were still alive. Only one patient developed grade III acute bowel toxicities but no grade III acute bladder toxicities or late grade II or above bowel or bladder toxicities were observed. Conclusion Salvage nodal radiation therapy alone to Fluorocholine PET/PSMA avid oligometasdtases of prostate cancer is a well tolerated, promising local treatment option for

hormone naive men with prior radical prostate treatment.

EP-1575 Radiotherapy for T3b prostate cancer (with seminal involvement) : clinical analyses F. Goupy 1 , E. Le Prisé 1 , D. Williaume 1 , C. Lafond 2 , A. Simon 3 , N. Perichon 2 , C. Hervé 2 , B. Leproust 4 , R. De Crevoisier 5 1 Centre Eugène Marquis, Radiotherapy, Rennes, France 2 Centre Eugène Marquis, Radiophysic, Rennes, France 3 LTSI- INSERM 1099, University Rennes 1, Rennes, France 4 Centre Eugène Marquis, Radiology, Rennes, France 5 Centre Eugène Marquis- LTISI- INSERM 1099, Radiotherapy and University Rennes 1, Rennes, France Purpose or Objective MRI can visualize invaded seminal vesicles (iSV) in prostatic cancer, classifying therefore the tumor stage as T3b. Delivering high curative dose (> 70 Gy) in the iSV is particularly challenging, when respecting the dose constraints in the OARs. The objective of this study was to analyze the clinical outcome of patients receiving radiotherapy for T3b prostate cancer. Material and Methods This retrospective analysis included all irradiated patients for T3b prostate cancer, between 2009 and 2016 in a single institution, with available MRI image and dosimetric data. MRI images were reviewed by a radiologist. A dosimetric analysis was performed. SV were divided in three thirds in the cranio-spinal axis. Recurrence and toxicities (CTCAE v4.0) were analyzed. Results A total of 96 T3b patients were included. Gleason scores were: 6 (5%), 7 (50%) and 8-10 (45%). The mean PSA was 24 ng/ mL. The SV invasion was at least in their proximal third (100%), two-thirds (35%), all (18%) and both SV (41%). Lymph nodes were found in 22% of the patients. The median total dose delivered to the prostate by IMRT was 78 Gy (range: 74-80). High-dose CTV included the iSV in 66%, 59% and 0% of cases only, when the SV invasion was in their proximal third, two thirds and all the SV, respectively. Median follow-up was 26 months (6-84). Three-year biological and clinical recurrence rates were 14% (95% CI: 5-23%) and 7% (95% CI: 0-14%), respectively. Acute GI and GU grade 3 toxicity rates were 0% and 2.3%. Three-year GI and GU grade > 2 toxicity rates were 5% (95% CI: 0-10%) and 18% (95% CI: 9-27%). Five patients had late grade 3 toxicity. Conclusion High dose irradiation for T3b prostate cancer leads to moderate toxicity. A multicentric study with larger follow-up is ongoing. EP-1576 Clinical Outcomes of 3D CRT with HDR brachytherapy in patients with localized Prostate cancer. M. Rafi 1 1 Sindh Institute of urology and Transplantation SIUT, Radiation Oncology, Karachi, Pakistan Purpose or Objective The purpose of this study was to evaluate and report the outcome of High dose rate (HDR) brachytherapy with conformal external beam radiotherapy (EBRT) in patients with localize prostate cancer. Material and Methods A total 480 patients with localized carcinoma of prostate cancer (T2b-T4a) were treated with the three dimensional conformal radiotherapy plus ultrasound