ESTRO 2021 Abstract Book

S1119

ESTRO 2021

Conclusion A low α/β (1.5 Gy) for late urinary toxicity resulted in higher likelihoods, consistently with a high sensitivity of late urinary tox to fractionation. This points out that hypofractionation should to be coupled to optimisation in the bladder-PTV overlap/urethra in order to reduce the risk of late urinary tox, especially for patients having other risk factors Funding: AIRC Investigator Grant, no.IG13090 and no. IG16087 PO-1364 Bleeding Risk after Prostate SBRT in Men on Baseline Anticoagulant/Antiplatelet Therapy A. Pepin 1 , S. Shah 2 , M. Pernia 3 , S. Lei 1 , M. Ayoob 1 , M. Danner 1 , T. Yung 1 , B. Collins 1 , S. Suy 1 , N. Aghdam 4 , S. Collins 1 1 Georgetown University, Radiation Medicine, Washington, USA; 2 George Washington University, School of Medicine and Health Sciences, Washington, USA; 3 George Washington University, Geriatrics, Washington, USA; 4 Beth Israel Deaconess, Radiation Oncology, Boston, USA Purpose or Objective Patients on anticoagulant/antiplatelet medications are at a high risk of bleeding following external beam radiation therapy for localized prostate cancer (Choe 2010). SBRT may reduce the bleeding risk by decreasing