ESTRO 2021 Abstract Book

S1120

ESTRO 2021

the volume of bladder/rectum receiving high doses. This retrospective study sought to evaluate the rates of hematuria and hematochezia following SBRT in these patients. Materials and Methods Localized prostate cancer patients treated with SBRT from 2007 to 2017 on at least one anticoagulant/antiplatelet at baseline were included. The minimum follow-up was 3 years with a median follow-up of 72 months. Patients who had a rectal spacer placed prior to SBRT were excluded. Radiotherapy was delivered in 5 fractions to a dose of 35 Gy or 36.25 Gy utilizing the CyberKnife system. Hematuria and hematochezia were prospectively assessed before and after treatment using the Expanded Prostate Cancer Index Composite (EPIC-26). Toxicities were scored using the CTCAE v4. Cystoscopy and colonoscopy findings were retrospectively reviewed. Results Forty-four men with a median age of 72 years with a history of taking at least one anticoagulant and/or antiplatelet medication received SBRT. Warfarin (46%), clopidogrel (34%) and rivaroxaban (9%) were the most common medications. Overall, 18.2% experienced hematuria with a median time of 10.5 months post- SBRT. Altogether, 38.6% experienced hematochezia with a median time of 6 months post-SBRT. > Grade 2 hematuria and hematochezia occurred in 4.6% and 2.5%, respectively. On patient required bladder neck fulguration and one patient underwent rectal cauterization for multiple non-confluent telangiectasia. There were no grade 4 or 5 toxicities. Cystoscopy revealed bladder cancer (50%) as the most common hematuria etiology. Colonoscopy demonstrated hemorrhoids (54.5%) and proctitis (9.1%) as the main causes of hematochezia. There was no significant change from the mean baseline EPIC-26 hematuria and hematochezia scores at any point during follow up. Conclusion In patients with baseline anticoagulant usage, moderate dose prostate SBRT was well tolerated without rectal spacing. High grade bleeding toxicities were uncommon and resolved with time. Baseline anticoagulation usage should not be considered a contraindication to prostate SBRT. PO-1365 Real time dynamic LDR Brachytherapy boost to external beam radiotherapy in prostate cancer S. Forner 1 , E. Xing 2 , S. Ravindra 1 , A. D'Souza 1 , F. Leach 1 , S. Nagpal 1 , T. Guerrero Urbano 3 , V. Mullassery 3 , O. Elhage 4 , R. Popert 4 , S. Morris 1 1 Guy's Cancer Centre, Guy's and St Thomas' NHS Foundation Trust, Clinical Oncology, London, United Kingdom; 2 Royal Free Hospital, Medicine, London, United Kingdom; 3 Guy's Cancer Centre, Guy's and St Thomas' NHS Foundation Trust, Clinical Oncology , London, United Kingdom; 4 Guy's and St Thomas' NHS Foundation Trust, Urology, London, United Kingdom Purpose or Objective Following the reports of the ASCENDE-RT trial we report a service evaluation of LDR brachytherapy as a boost to EBRT for patients with prostate cancer. Materials and Methods Retrospective review of patients treated with an LDR brachytherapy boost to EBRT between 2008 and 2018. LDR brachytherapy was carried out as a single stage day case procedure using a real time dynamic procedure prescribed to a dose of 110 – 115Gy, EBRT was delivered with IMRT and soft tissue matching IGRT to the prostate and SV +/- pelvic nodes to a dose of 46Gy/23#. We collected outcomes on overall survival and relapse. Late GU and GI Toxicity was scored using LentSoma. Results 139 patients were treated with Median age 64. 49 patients had high risk and 90 had intermediate risk disease. 49 patients received hormone therapy. Median follow-up of 52.4 months (range 3.5 to 129). The 5 year OS was 93.5%. The 5 year b-PFS was 84.4%. 9 patients have died, only 1 from prostate cancer. 14 patients have relapsed of which 6 biochemical relapse only, 6 lymph node and 2 bone metastases. Late grade 3 GU toxicity incidence 6.5% (prevalence 2.2%), late grade 2 GI toxicity incidence 16.5%, grade 3 0.7%. 1 patient had a grade 4 recto-vesical fistula related to a rectal biopsy. Acute retention rate requiring catheterisation was 2.2%. The rate of urethral stricture requiring dilatation was 2.2%. Conclusion Our experience shows that the LDR brachytherapy as a boost to EBRT is highly effective and with modern brachytherapy techniques has a low incidence of toxicity. PO-1366 Pattern of recurrence after SBRT in prostate cancer patients with nodal pelvic relapse G. Francolini 1 , C. Bellini 2 , V. Di Cataldo 3 , B. Detti 1 , A. Bruni 4 , G. Alicino 5 , L. Triggiani 6 , S. La Mattina 6 , R.M. D'Angelillo 7 , C. Demofonti 7 , R. Mazzola 8 , F. Cuccia 8 , F. Alongi 8 , M. Aquilano 2 , A.G. Allegra 2 , L.P. Ciccone 2 , G. Stocchi 2 , V. Salvestrini 2 , B. Guerrieri 2 , L. Livi 2 1 Azienda Ospedaliera Universitaria Careggi, Radiotherapy Unit, Florence, Italy; 2 University of Florence, Department of Experimental and Clinical Biomedical Sciences "M. Serio", Florence, Italy; 3 Istituto Fiorentino di Cura e Assistenza (IFCA), Radiotherapy Unit, Florence, Italy; 4 Modena Hospital, Radiation Oncology Unit, Modena, Italy; 5 Radiation Oncology Unit, Modena Hospital, Modena, Italy; 6 University and Spedali Civili Hospital, Department of Radiation Oncology, Brescia, Italy; 7 Policlinico Tor Vergata University, Department of Radiation Oncology, Rome, Italy; 8 IRCCS, Sacro Cuore Don Calabria Hospital, Negrar, Radiation Oncology Department, Verona, Italy Purpose or Objective Salvage radiotherapy is the main treatment option for biochemical relapse (BCR) after radical prostatectomy (RP). However, novel imaging methods allowed to increase staging sensibility in BCR setting, with Choline and PSMA PET showing a detection rate of 86-93% and 33-99%, respectively, depending on PSA values. Currently, when nodal pelvic oligorecurrent disease is detected, no standard treatment option is recommended, and comparative data between different management strategies are lacking. One possible salvage option is nodal