ESTRO 2020 Abstract Book

S625 ESTRO 2020

Conclusion The gene signature in the present study is a powerful predictor and risk factor for BCR after radical prostatectomy. PO-1188 Optimal radiotherapy strategy as risk-group in non-metastatic prostate cancer patients (KROG 18-15) S.H. Choi 1 , Y.S. Kim 2 , J. Yu 2 , T. Nam 3 , J. Kim 4 , B. Jang 4 , J.H. Kim 5 , Y. Kim 6 , B.K. Jung 7 , A.R. Chang 8 , Y. Park 8 , S.U. Lee 9 , K.H. Cho 9 , J.H. Kim 10 , H. Kim 11 , Y. Choi 12 , Y.J. Kim 13 , D.S. Lee 14 , Y.J. Shin 15 , S.J. Shim 16 , W. Park 17 , J. Cho 1 1 Yonsei Cancer Center- Yonsei University College of Medicine, Department of radiation oncology, Seoul, Korea Republic of ; 2 Asan Medical Center, Department of Radiation Oncology, Seoul, Korea Republic of ; 3 Chonnam National University Hwasun Hospital, Department of radiation oncology, Hwasun, Korea Republic of ; 4 Seoul National University Bundang Hospital, Department of radiation oncology, Bundang, Korea Republic of ; 5 Seoul National University Hospital, Department of radiation oncology, Seoul, Korea Republic of ; 6 Kyung Hee University Hospital, Department of radiation oncology, Seoul, Korea Republic of ; 7 School of Medicine- Gyeongsang National University, Department of radiation oncology, Chang won, Korea Republic of ; 8 Soonchunhyang University Seoul Hospital, Department of radiation oncology, Seoul, Korea Republic of ; 9 The Proton Therapy Center- Research Institute and Hospital- National Cancer Center, Department of radiation oncology, Ilsan, Korea Republic of ; 10 Keimyung University Dongsan Medical Center- Keimyung University School of Medicine, Department of radiation oncology, Daegu, Korea Republic of ; 11 Inha University Hospital- Inha University School of Medicine, Department of radiation oncology, Incheon, Korea Republic of ; 12 Dong-A University Hospital- Dong-A University School of Medicine, Department of radiation oncology, Pusan, Korea Republic of ; 13 Kangwon National University Hospital, Department of radiation oncology, Chuncheon, Korea Republic of ; 14 The Catholic University of Korea- Uijeongbu, Department of radiation oncology, Uijeongbu, Korea Republic of ; 15 Inje University Sanggye Paik Hospital, Department of radiation oncology, Inje, Korea Republic of ; 16 Eulji Hospital- Eulji University School of Medicine, Department of radiation oncology, Seoul, Korea Republic of ; 17 Samsung Medical Center- Sungkyunkwan University School of Medicine, Department of radiation oncology, Seoul, Korea Republic of Purpose or Objective External beam radiotherapy (EBRT) is evolving with numerous strategies incorporated to improve outcomes, and several studies showed an improvement in outcome by increasing the radiation dose in prostate cancer. Nevertheless, the optimum dose and fractionation scheme for each NCCN risk group is still unclear. The aim of Korean Radiation Oncology Group (KROG) 18-15 study was to validate the NCCN classification in multi-institutional large cohort and find the optimal EBRT strategy in each risk group. Material and Methods Non-metastatic prostate cancer patients who underwent definitive RT between 2001 and 2015 were eligible for this study. A total of 1,854 patients in 17 institutions were included and all were re-grouped in accordance with the NCCN Version 2.2019 guideline risk groups. Biochemical failure (BCF) was defined as nadir +2 ng/mL or the initiation of ADT for increasing PSA regardless of its value. The BCF-free survival (BCFFS), overall survival (OS) rates were estimated and radiation-related toxicities were evaluated according to the RTOG criteria.

Results The numbers of each risk group patients were as follows: low 181 (10%), intermediate 425 (23%), high 799 (43%), very high 239 (13%), and N+ 210 (11%). Intensity-modulated RT (IMRT) was done in 74%, and hypofractionation (HF) or ultra-HF were selected in 47% and 9%, respectively. The irradiated dose was median biologically effective dose (BED) 179.1 (range, 97.7-225.0) Gy 1.5 . With a median follow-up of 73 months, the 5- and 10-year BCFFS rates were 81% and 58%, and OS rates were 95% and 83%, respectively. Significantly differentiated prognosis was shown as NCCN risk groups. (5-yr BCFFS: 92%, 84%, 81%, 76%, and N+ 63%, p<0.001; BCF rate: 8%, 15%, 21%, 26%, and N+ 38%, p<0.001). In the univariate analysis for BCFFS, stage, Gleason score, RT modality, dose, and fractionation scheme were significant factors. There was a significant linear relationship between BED and BCFFS (p=0.032), with 179 Gy 1.5 (EQD2 77 Gy) being the most significant cut-off. In the multivariate analysis, ADT, IMRT, and ≥179 Gy 1.5 were still associated with better BCFFS (all Ps<0.05). Although there was no significant factor in low-risk group, slightly higher dose (≥170 Gy 1.5 ) and HF were significant factors in intermediate-risk group (p=0.02, 0.034). In high- risk group, ADT and ≥179 Gy 1.5 were independently significant factors (p<0.001, 0.009). The rate of toxicity (≥grade II) was acceptable (acute GU 11%, acute GI 7%, late GU 13%, late GI 7%, urinary incontinence 7%, impotence 5%), although acute GI and late GU toxicity could be increased with whole pelvis RT (all Ps<0.001). Conclusion Based on a large multi-institutional cohort of Korea, EBRT was an effective and noninvasive treatment option for non-metastatic prostate cancer and the most recent NCCN risk classification proved to be a useful predicting tool. In the era of patient stratification, differentiated RT dose in each risk group (higher dose in high risk group) should be selected. Modern RT techniques (HF, IMRT) will effectively deliver higher doses without increasing severe toxicities. PO-1189 VMAT SBRT for localized prostate cancer: 5- year update on toxicity and survival G.R. D'Agostino 1 , L. Di Brina 1 , C. Franzese 1 , C. Iftode 1 , P. Mancosu 1 , F. De Rose 1 , E. Clerici 1 , G. Reggiori 1 , M. Badalamenti 1 , M. Scorsetti 1 1 Humanitas Research Hospital, Radiotherapy and Radiosurgery, Rozzano Milan, Italy Purpose or Objective This study updates our previously reported experience on the safety and efficacy of a Linac-based stereotactic body radiotherapy (SBRT) in patients with low or intermediate risk prostate cancer. Material and Methods Biopsy confirmed prostate cancer patients were enrolled, provided that they had the following characteristics: initial PSA <20ng/ml, Gleason Score <8, IPSS <8. The treatment schedule was 35 Gy in 5 fractions, delivered every other day, with volumetric modulated arc therapy and flattening filter free beams. Toxicity was recorded according to CTC-AE criteria v3.0. Biochemical failure was calculated according to the Phoenix criteria. Results Between February 2011 and March 2015, 90 patients were enrolled (53 low risk, 37 intermediate risk, according to the NCCN criteria). The median age was 71 years (range 48–82). The median initial PSA was 6.98 ng/ml (mean 7.18, range 2.7–17.0). According to the ISUP - WHO 2016 Grading System 53 patients (58.9%) had a Grade Group (GG) 1, 24 patients (26.7%) a GG 2 and 13 patients (14.4%) a GG 3 prostate cancer. Acute toxicity was mild, and already reported. Urinary late toxicity, represented by urgency and/or dysuria, was G1 in 45 patients (50.0%), G2 in 3 patients (3.3%). A G1 late proctitis was recorded in 17 patients (18.9 %). One patient (1.1%) experienced a G2 rectal hemorrhage.