ESTRO 2020 Abstract book

S666 ESTRO 2020

PO-1175 SBRT for localised prostate cancer – Nordic results with mFU of 5.3 years K. Vuolukka 1 , J. Palmgren 1 , E. Tiainen 2 , H. Janne 1 , P. Auvinen 1 , V. Kataja 3 , J. Seppälä 1 1 Kuopio University Hospital, Center of Oncology, Kuopio, Finland ; 2 University of Eastern Finland, Faculty of medicine, Kuopio, Finland ; 3 Central Finland Central Hospital, Administration, Jyväskylä, Finland Purpose or Objective The use of hypofractionated stereotactic body radiotherapy (SBRT) as primary treatment modality in clinically localized prostate cancer (PCa) is emerging. There is a need for more data about the efficacy and toxicity of SBRT, especially in high-risk PCa patients. The purpose of this retrospective study was to up-date the safety and the efficacy results of the first Nordic PCa patient cohort treated with robotic SBRT. Material and Methods During the years 2012-2015, 218 consecutive patients with clinically localized PCa were treated with SBRT to total doses of 35 Gy or 36.25 Gy in 5 fractions using a robotic SBRT device (CyberKnife® VSI). The incidences of grade 3 genitourinary (GU) and rectal (GI) toxicities and overall survival (OS), disease-specific survival (DSS) and biochemical relapse-free survival (bRFS) were analysed. Patients with only one PSA (n=5) after SBRT were excluded from the analysis. Results A total of 213 patients were included to the analysis. The median age was 70 years (range, 47-86 years). The number of patients with a low-, intermediate- and high-risk PCa were 48 (22.5%), 56 (26.3%) and 109 (51.2%), respectively. At the cut-off, the median follow-up (mFU) was 64 months (range, 10-85 months), the OS rate was 91.5%, DSS rate 99.1% and the bRFS rate 87.8%. Efficacy results according to the risk groups are presented in Table 1. The 4-year bRFS rates were 100%, 96% and 96% in low, intermediate and high-risk groups, respectively. There were no significant differences in efficacy parameters according to the total dose or PSA. However, the bRFS correlated significantly to the Gleason Score ( p =0.000), the risk-group ( p =0,012) and the use of ADT ( p =0,006). Table 2 . The incidence of severe (grade 3) GU and GI toxicities were 4.2% (n=9) and 0.9% (n=2), respectively. Table 1. Efficacy results according to D’Amico risk groups.

Conclusion To the best of our knowledge, this study includes the largest single center European cohort of patients with localized PCa treated with robotic SBRT. It also includes one of the largest cohorts of high-risk patients (n=109, 51.2%) treated with this ultrahypofractionated mode of radiation therapy. With the mFU of 5.3 years, the efficacy results are promising in all risk groups and the toxicity is low. However, larger studies with longer follow-up times are needed to proof the robustness of the SBRT as one of the primary treatment modalities in localized PCa. PO-1176 Ultra-hypofractionated SBRT for localized prostate cancer: single institution experience A. Acosta Rojas 1 , A. Montero Luis 1 , J. Valero Albarran 1 , O. Hernando Requejo 1 , E. Sanchez Saugar 1 , R. Ciervide Jurio 1 , M. Garcia-Aranda 1 , X. Chen 1 , R. Alonso Gutierrez 1 , M.A. De la Casa 2 , D. Zucca 2 , P. Fernandez Leton 2 , M.C. Rubio Rodriguez 1 1 University Hospitals Madrid Sanchinarro & Madrid Puerta del Sur, Radiation Oncology, Madrid, Spain ; 2 University Hospitals Madrid Sanchinarro & Madrid Puerta del Sur, Medical Radiation Physics, Madrid, Spain Purpose or Objective To evaluate clinical outcomes and tolerance toxicity for localized prostate cancer treated by ultra- We reviewed 104 patients with a median age of 70yo (52- 82) diagnosed with low (51.92%), intermediate (47.12%) and high risk (0.96%) prostate cancer treated with a definitive-intent SBRT between 2016-2019. Patients´ characteristics are detailed in image 1. Dose prescription for the entire cohort was 36.25Gy in 5 fractions of 7.25Gy on every-other-day. Treatments were delivered in a lineal accelerator Novalis (Brainlab) with daily inter and intra-fraction orthogonal- Xray image guidance (Exactrac®) in 85p (81.73%). All had two gold-fiducials markers placed transperineally into the prostate guided by transrectal-ultrasound and endorectal hypofractionated SBRT. Material and Methods

Table 2. Biochemical relapse-free survival (bRFS) rates in different subgroups at the cut-off.