ESTRO 2020 Abstract Book

S616 ESTRO 2020

Results With a median follow-up of 109 months (range 16-248) for LTL and 108 months (24-210) for NTL (p=ns), 90 patients (38%) with LTL had died compared with 44 patients (16%) in NTL group. The 9-year DFS, OS and CSS for LTL were 76%, 72% and 93% and 94% (p=0.000), 89% (p=0.000) and 99% (p=0.000) in NTL respectively. In the multivariate analysis NTL was a significant predictor of DFS (p=0.000), OS (p=0.004) and CSS (p=0.002), age of OS (p=0.000) and tumour stage and cardiovascular disease of DFS (p=0.018) Regarding our results, patients with long-term LTL had lower survivals and higher cause of death than NTL, in probable relationship with more advanced and aggressive disease at baseline, and older age where competitive comorbidities are also high. PO-1171 Low- and Intermediate-Risk Prostate Cancer. Stereotactic Body Radiation Therapy. Our experience. C. García Aguilera 1 , A. Méndez Villamón 1 , S. Flamarique Andueza 1 , D. Villa Gazulla 1 , C. Escuín Troncho 1 , J.M. Ponce Ortega 1 , M.M. Puertas Valiño 1 , M. Tejedor Gutiérrez 1 1 Hospital Universitario Miguel Servet, Servicio de Oncología Radioterápica, Zaragoza, Spain Purpose or Objective To analyze the survival and toxicity of patients with low and intermediate risk prostate cancer treated with Stereotactic Body Radiotherapy (SBRT) in our center. Material and Methods We retrospectively included patients with low and intermediate risk prostate cancer treated with SBRT between February 2014 and July 2019. We analyzed progression-free survival, prostate cancer-specific survival and actuarial overall survival. To measure toxicity, acute and late, we used the CTCAE 4.0 scale. We analyze 253 patients, 35,6% were low risk and 64.04% intermediate risk. 39,9% had hormonal treatment (analogue LHRH) in short cycle (6 months). We perform simulation CT. To minimize doses in risk organs, the patients was advised dietematically and bladder preparation was performed. The treatment was administered with intensity-modulated radiotherapy using linear accelerator, guided by daily image by megavoltage cone-beam. The dose used was 35Gy in 5 fractions of 7Gy, one day a week on the volume of the prostate. (p=0.038). Conclusion

Results With a mean follow-up of 20 months, we estimated that the progression-free survival was 98,7%. Cancer-specific global survival was 100%, while actuarial overall survival was 95,8% None of our patients experienced acute or late grade 3 toxicity. 53,36% had acute genitourinary grade 1 (GU) and 5,53% grade 2 GU. 11,86% reported acute gastrointestinal toxicity (GI) and 1.01% grade 2 GI. Late toxicity grade 1 GU 3,56% and GI 11,86%.

Conclusion Stereotactic body radiation therapy administered with linear accelerator, in patients with low and intermediate risk prostate cancer is effective, achieving good control of the disease and toxicity profile. PO-1172 dose effects due to interfractional variability for hypofractionated radiotherapy of prostate cancer M. Splinter 1,2,3 , I. Sachpazidis 4 , T. Bostel 3,5 , P. Häring 1,2,3 , C. Lang 1,2,3 , A. Grosu 4 , J. Debus 2,3,6 , D. Baltas 4 , N.H. Nicolay 3,4 1 German Cancer Research Center DKFZ, Division of Medical Physics in Radiation Oncology- E040, Heidelberg, Germany ; 2 Heidelberg Institute for Radiooncology, National Center for Radiation Research in Oncology, Heidelberg, Germany ; 3 German Cancer Research Center DKFZ, Clinical Cooperation Unit "Radiation Oncology", Heidelberg, Germany ; 4 Freiburg University Medical Center, Department of radiation Oncology, Freiburg, Germany ; 5 Mainz University Medical Center, Department of radiation Oncology, Mainz, Germany ; 6 University