ESTRO 2022 - Abstract Book

S501

Abstract book

ESTRO 2022

visual inspection of the volumes, the greatest areas of disagreement appear to be at the inferior and superior extent and the cranial aspect of the anterior border.

Conclusion Despite minimal experience in MR contouring for prostate bed, the agreement between the radiation/clinical oncologists as demonstrated by the median DICE metric is reasonable. The DICE metric however tends to be more generous for the same absolute error for larger volumes as opposed to smaller volumes. The distance metrics show greater variability amongst observers whilst the volume measurement shows the greatest variability. Outliers are not uncommon. As a group, we have reviewed and discussed the contours with contribution from radiology and surgical colleagues and will be creating consensus guidelines for contouring the prostate bed CTV on MR.

PD-0572 Ten-year outcomes of post prostatectomy radiotherapy and external validation of an updated nomogram

S. Chin 1,2,3 , P. Horsley 4 , H. Mistry 5 , N. Aherne 1,4 , T. Shakespeare 1,4

1 University of New South Wales, Rural Clinical School, Coffs Harbour, Australia; 2 La Trobe University, Olivia Newton John Cancer Research Institute, Heidelberg, Australia; 3 University of Melbourne, Surgery at Austin Health, Heidelberg, Australia; 4 Mid North Coast Cancer Institute, Radiation Oncology, Coffs Harbour, Australia; 5 The University of Manchester, Division of Pharmacy and Cancer Sciences, Manchester, United Kingdom Purpose or Objective Long term tumour control outcomes have not been published for post prostatectomy radiation therapy (PPRT) to the prostate bed using Australian contouring guidelines. We report 10 year outcomes after PPRT using Australian contouring guidelines and externally validated a recently updated nomogram (Campbell et al. 2021) predicting biochemical failure (BF) after salvage radiation therapy (SRT) incorporating PSA kinetics. Materials and Methods A retrospective review was performed for 293 men treated with image guided intensity modulated radiation therapy to the prostate bed with 64-66Gy in 32-33 fractions for pT2-4 R0-1 N0/X M0 prostate adenocarcinoma. Freedom from biochemical failure (FFBF), distant metastasis (DM), cancer-specific mortality (CSM), and overall survival (OS) were analysed from