ESTRO 38 Abstract book

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(49.3%), T3a-b in 66 (47.1%) and not known in 5 (3.6%) patients, respectively. Median PSA value at the moment of PET/CT was 0.73 ng/ml (range 0.23-8.90); in particular, PSA was >0.2 and <0.5 ng/ml in 44 (31.5%), >0.5 e <1 ng/ml in 49 (35%), >1 and <1.5 ng/ml in 23 (16.4%) and >1.5 ng/ml in 24 (17.1%) patients, respectively. Median PSA doubling time and PSA velocity were 8.7 months (range 0.6-264.8) and 0.6 ng/ml/yr (range 0-30.2), respectively. 68 Ga-PSMA-11 PET/CT was considered positive in 57 cases (40.7%); recurrence was located in prostate bed (n=10), loco-regional lymph nodes (n=30), lymph nodes and bone (n=4), and distant sites (n=13). A significant association was observed for PSA velocity (median 0.9 in PET+ vs 0.35 ng/ml/yr in PET-, p<0.001), the 3 main risk factors for PET positivity were the last absolute PSA value before 68 Ga- PSMA PET/CT > 1 ng/ml (OR 5.64, 95% CI 2.23-14.26, p<0.001), a PSA dubling time ≤8,7 month (OR 3.13, 95% CI 1.53-6.42, p 0.002) and a T3 stage (OR 4.33, 95% CI 2.06- 9.10, p<0.001), both in univariate and multivariate logistic models. Patient management was modified in 29 cases (21%) on the basis of 68 Ga-PSMA-11 PET/CT findings. Conclusion Preliminary data suggest that 68 Ga-PSMA-11 PET/CT results may be clinically useful to detect prostate cancer recurrence at low PSA values, when dealing with the most aggressive disease patterns. In this setting, a proper selection of the patients that could really benefit of 68 Ga- PSMA-11 PET/CT is mandatory, in order to reach a more cost-effective profile. Larger prospective trials are needed. PO-0836 Outcomes and factors by risk group after prostate brachytherapy: Cohort study in 2316 patients N. Katayama 1 , K. Nakamura 2 , A. Yorozu 3 , T. Kikuchi 4 , T. Magome 5 , S. Saito 6 , T. Dokiya 7 , M. Fukushima 8 , S. Kanazawa 1 1 Okayama University Hospital, Department of Radiology, Okayama, Japan ; 2 Hamamatsu University School of Medicine, Department of Radiation Oncology, Hamamatsu, Japan ; 3 National Hospital Organization Tokyo Medical Center, Department of Radiation Oncology, Tokyo, Japan ; 4 Translational Research Center for Medical Innovation, Department of Statistics, Kobe, Japan ; 5 Komazawa University, Department of Radiological Sciences- Faculty of Health Sciences, Tokyo, Japan ; 6 National Hospital Organization Tokyo Medical Center, Department of Urology, Tokyo, Japan ; 7 Kyoundou Hosipital, Department of Radiology, Tokyo, Japan ; 8 Translational Research Center for Medical Innovation, Director and Chairman, Kobe, Japan Purpose or Objective The nationwide prospective cohort study in Japan (J- POPS) resulted in excellent biochemical freedom from failure (bFFF) among all patients who were treated during the first 2 years. Here we report the bFFF by risk group and treatment modality and the associated factors of bFFF by risk group in those patients with prostate cancer undergoing permanent seed implantation (PI) with or without external beam radiation therapy (EBRT). Material and Methods A total of 2,316 patients in 42 institutes were evaluated. BFFF was evaluated using the Phoenix definition (prostate- specific antigen (PSA) nadir + 2.0 ng/mL). If the PSA subsequently fell to ≤0.5 ng/mL without intervention, this was considered a PSA bounce. The scheduled follow-up assessments were conducted every 3 months for the first 2 years, and every 6 months thereafter for 5 years after completion of radiation therapy. We estimated the bFFF by the Kaplan Meier method. We also identified the factors associated with the bFFF by the Cox proportional hazard

from the cone beam CT (CBCT) Scans. At the end of the exercise, patients were asked to fill in a quality of life questionnaire (EORTC QLQ-PR25) prior to RT, half-way through RT, on the day of the last fraction of RT and at 3 and 6 months after RT to assess side effects. Radiotherapy was performed using 10 or 6 MV photons delivered from a Varian 2100IX linear accelerator. Treatment planning was performed on the ‘Eclipse’ system using CT scans. A dose of 74 Gy in 37 fractions was delivered. Every patient completed the prescribed treatment. Results There were no differences in the number of CBCT scans between group 1 (39.0 CBCT scans per patient) and group 2 (38.5 CBCT scans per patient). No differences were seen either in the reduction of bladder volumes between groups 1 and 2. The percentages of the bladder volume for group 1 and group 2 patients when compared to the pre-RT bladder volume were 81.8 % ± 25.2 and 80.2 % ± 37.9 respectively at week 4, and 84.7 % ± 35.7 and 76.5 % ± 34.1 respectively on the last day of RT. Finally, based on the answers from the quality of life questionnaire, no differences in early or late side effects were seen between both groups of patients. Conclusion Providing information on RT planning and delivery using 3D imaging systems rather than 2D helped patients and relatives to better understand the complexity of RT planning and delivery 1 . However, no differences were seen regarding patients’ compliance to RT or side effects from RT. 1. Sulé-Suso J., et al. Pilot study on virtual imaging for patient information on radiotherapy planning and delivery. Radiography 21: 273-277; 2015. PO-0835 68GaPSMA11 PET/CT in prostate cancer patients with biochemical recurrence: PET positivity predictors R. Parise 1 , S. Bartoncini 1 , A. Guarneri 1 , D. Deandreis 2 , B. Lillaz 3 , S.D. Solla 1 , L. Spinelli 1 , D. Nicolotti 2 , E. Pilati 2 , M. Bellò 2 , R. Passera 2 , P. Gontero 3 , G. Bisi 2 , U. Ricardi 1 1 A.O.U. Città della Salute e della Scienza, Oncology- Radiation Oncology, Torino, Italy ; 2 A.O.U. Città della Salute e della Scienza, Medical Sciences- Nuclear Medicine Unit, Torino, Italy ; 3 A.O.U. Città della Salute e della Scienza, Surgical Sciences- Division of Urology, Torino, Italy Purpose or Objective 68 Ga-PSMA-11 PET/CT is nowadays the most promising PET tracer in the detection of prostate cancer recurrence. The aim of this study is to assess the detection rate of this technique in patients with prostate cancer biochemical recurrence (BCR) with low PSA levels, and to evaluate which are the predictors of PET positivity. Material and Methods We prospectively enrolled patients referred to our Center between November 2016 and March 2018 with BCR, after primary treatment. All patients underwent 68 Ga-PSMA-11 PET/CT; in case of PSA >1.5 ng/ml the exam was performed only if previous choline PET/CT were negative. Clearly positive 68 Ga-PSMA-11 PET/CT findings were considered as true positive; dubious findings were explored by other imaging techniques and defined as true positive or true negative by a multidisciplinary consensus. Association between PET positivity and clinical patterns was evaluated by univariate and multivariate logistic regression models. Results A total of 140 68 Ga-PSMA-11 PET/CT scans were performed; in 76 (54.3%) patients after radical surgical treatment only, in 3 (2.1%) patients after radiotherapy only and in 61 (43.6%) patients after radical surgery and adjuvant or salvage radiotherapy. Gleason Score (GS) was ≤3+4 in 59 (42.1%), ≥4+3 in 78 (55.8%) and not known in 3 (2.1%) patients, respectively. T stage was T1C-T2b-c in 69

model. Results

The median age was 69.0 (range, 45-89) years. Median PSA was 6.8 (range, 1.6-42.0) ng/ml. 2,103 patients (23.4%)