ESTRO 2022 - Abstract Book

S681

Abstract book

ESTRO 2022

Results Pathological nodes on imaging at diagnosis was found in 66/135 (49%) with a range of 1-7 nodes per patient. Total number of nodes treated with SIB was 184 of which 20 (11%) were para-aortic. 91% of the nodes were PET-CT positive. Median follow-up time was 20 months. Six patients had SIB node recurrence. In total 7 (4%) SIB nodes recurred resulting in a 3-year actuarial SIB control rate of 93%. All recurrent SIB nodes were located in the pelvis and all were PET-CT positive at diagnosis. Median nodal volume was 2.0 and 4.2 cm 3 in controlled and recurrent SIB nodes, respectively. Only one of the patients with a recurring SIB node had received Cisplatin. Conclusion Despite a low completion rate of concomitant cisplatin, this study demonstrates a satisfying long-term control rate of pathological nodes treated by CovP based SIB in unselected patients with LACC. The results lend support to the utilization of CovP for SIB of both pelvic and para-aortic nodes. Confirmation is awaited from the EMBRACE II study.

References 1) Ramlov, Radiother Oncol, 2017, 123:158-163 2) Pötter, Clin Transl Radiat Oncol, 2018, 9:48-60 3) Lindegaard, Acta Oncologica, 2017, 56:1479-1486

OC-0765 Genitourinary hrQoL following Urethral sparing prostate SBRT compared with virtual HDR boost.

M. Richardson 1 , M. Sidhom 2,3 , P. Keal 4 , J. Bucci 5,3 , S. Gallagher 1 , P. Greer 1,6 , A. Hayden 7 , A. Kneebone 8,9 , D. Pryor 10,11 , S. Siva 12 , J. Martin 1,13 1 Calvary Mater Newcastle, Radiation Oncology, Newcastle, Australia; 2 Liverpool Cancer Therapy Centre, Radiation Oncology, Sydney, Australia; 3 University of New South Wales, Faculty of Medicine, Sydney, Australia; 4 The University of Sydney, ACRF Image X Institute, Sydney, Australia; 5 Cancer Care Centre, St George Hospital, Sydney, Australia; 6 University of Newcastle, School of Mathematical and Physical Science, Newcastle, Australia; 7 Westmead Hospital, Radiation Oncology, Sydney, Australia; 8 The University of Sydney, Faculty of Medicine and Health, Sydney, Australia; 9 Royal North Shore Hospital, Radiation Oncology, Sydney, Australia; 10 Princess Alexandria Hospital, Radiation Oncology, Brisbane, Australia; 11 School of Chemistry and Physics, Queensland University of Technology, Woolloongabba, Australia; 12 Peter MacCallum Cancer Centre, Division of Radiation Oncology and Cancer Imaging, Melbourne, Australia; 13 University of Newcastle, School of Medicine and Public Health, Newcastle, Australia Purpose or Objective Urinary symptoms after prostate radiotherapy have a measurable impact on patient quality of life. Limiting dose to the prostatic urethra is an emerging technique for prostate SBRT. We present EPIC-26 GU health related quality of life (hrQoL) outcomes 3 years post urethral sparing SBRT (US-SBRT), comparing a 5 fraction SBRT approach with an SBRT + EBRT boost alternative. Materials and Methods We compared prospective data from two multicentre, phase 2 clinical trials of US-SBRT. The SPARK trial (ACTRN12615000335594) prescribed 36.25 Gy/5fx to the prostate (SBRT). The PROMETHEUS trial (ACTRN12615000223538) utilised an SBRT boost (19-20 Gy/2fx) combined with fractionated EBRT (46 Gy/23fx or 36 Gy/12fx). The biological equivalent dose (BED) for urethral toxicity ( α / β =3) for the SBRT cohort was 123.9 Gy, and 155.8–171.2 Gy for the SBRT+EBRT cohort. A urethra PRV was defined as a 1mm radial margin from urinary catheter, or estimated from MRI +3mm radially. Urethra PRV dose limits were applied such that for SBRT and SBRT+EBRT Dmax was 0.1cc ≤ 107% and <110% respectively, and V105% TD <5% in both cohorts. Patients completed an EPIC-26 questionnaire at baseline and then repeated up to 36 months post RT. Comparisons between cohorts were performed. We recorded any minimal clinically important change (MCIC) of >0.5 standard deviation decrease from baseline score. Results EPIC scoring was completed at baseline by 45 SBRT patients (96% intermediate, 4% low-risk) with a median age of 69 (range 57-81), and 160 SBRT + EBRT patients (76% intermediate, 24% high-risk) with a median age of 70 years (range 53–81). Independent two-tailed t-tests revealed statistically inferior urinary incontinence in the SBRT+EBRT cohort at baseline (p=.04) that continued across all time points. For irritative/obstructive outcomes, significant differences were identified at 12 and 36 months (87.2 v 79.8 and 94.2 v 86.5, both p=0.01) in favour of the SBRT cohort (Fig 1).