ESTRO 2021 Abstract Book

S1086

ESTRO 2021

Purpose or Objective This is a retrospective study conducted to report the tumor control and toxicity outcomes of patients with intermediate-risk prostate cancer treated with external beam radiotherapy (EBRT) and LDR-PB. We expect lower incidence of late genitourinary (GU) morbidity with real-time intraoperative planning in our series (vs pre-plan system used in ASCENDE-RT) with good results in biochemical progression-free survival (bPFS). Materials and Methods 88 patients(p)(years 2009-2018) received 44-46Gray(Gy) of EBRT to the prostate and seminal vesicles and a LDR-PB transperineal prostate implant of I125(110 Gy). Every patient received 6months of androgen deprivation therapy. Toxicity was graded using CTCAEv4.0. We analyzed (bPFS) and overall survival(OS) with Kaplan Meir. Analysis of acute-late toxicity (bleeding, frequency, pain, TURP...) with SPSSv25 Results Median follow-up was 5,2 years. The bPFS and prostate cancer-specific survival at 5 years were 100%. The incidence of acute and late toxicity is in table1. Only 3p (3,4%) had late GU-G3 toxicity (TURP or urethral dilatation). Table 2 shows the difference between our series and ASCENDE-RT series. Median D1ccUrethral:138Gy, median D2ccrectal: 66,08Gy

Conclusion Our series has shown a high bPFS and OS. In addition, the risk of toxicity is far lower than that reported by the ASCENDE-RT study. LDR-PB boost with real-time intraoperative planning is a safe and effective option for treatment patients with intermediate-risk prostate cancer. PO-1324 dose-volume correlation of pelvic bone normal tissue and hematocrit in patients with prostate cancer P. Papanikolaou 1 , G. Swanson 2 , S. Stathakis 1 , M. Fakhreddine 1 , P. Mavroidis 3 1 UT Health San Antonio MD Anderson Cancer Center, Radiation Oncology, San Antonio, Texas, USA; 2 Baylor Scott & White Health, Radiation Oncology, Temple, Texas, USA; 3 University of North Carolina Chapel Hill, Radiation Oncology, Chapel Hill, North Carolina, USA Purpose or Objective The purpose of this study was to model the correlation of radiation dose to different parts of the pelvis with a significant drop in hematocrit 3 months after prostate cancer radiotherapy. Materials and Methods A retrospective review was conducted on 221 patients receiving radiotherapy for prostate adenocarcinoma at a single institution from 2014-2016. Patients received either 78Gy to primary prostate or 70Gy post- prostatectomy, and most received 54Gy to the pelvic lymph nodes. All patients had complete blood counts (CBCs) collected at baseline (pre-RT) and 3 months post-RT. The net difference of each CBC metric post-RT vs. baseline was calculated and the level of the 15 percentiles defined the thresholds of response in each case. The doses to 8 different contoured pelvic structures were derived and fitted to 20 CBC metrics using the