ESTRO 2024 - Abstract Book

S2343

Clinical - Urology

ESTRO 2024

57 patients received androgen deprivation therapy, 31 with LHRH agonist and 26 with oral anti-androgen. Median duration of ADT was 6 months. 20 patients had insertion of rectal spacer at time of fiducial marker insertion. Median PSA at 12 months post SABR was 0.8ng/ml. Median PTV volume was 81.3cm³, range 46.4 – 167.8cm³. Median OAR volume for rectum was 65.3cm³ and bladder was 250.2cm³. Dose constraints as per PACE B were met in 96.7% of patients; V18Gy for rectum and bladder were met in 100%, V37Gy for bladder in 96.7% and V29Gy for rectum in 98.9%. PTV constraints were met in 100% of patients. Toxicity was graded using CTCAEv5. Median time to peak GI/GU acute toxicity was 1 week post final fraction. G2 GI toxicity occurred in 21% of patients at week 1, 12.2% at week 2 and 2.2% at week 4 post radiotherapy. One patient experienced G2 GI toxicity in week 3. G2 GU toxicity occurred in 3.3% of patients in week 1 and 2, and 2.2% at week 4. One patient experienced G3 GU toxicity in week 4 (note coincident kidney stone). No patient experienced G4 toxicity.

Our acute toxicity results are comparable with those reported in the PACE B clinical trial.

Conclusion:

Our results demonstrate that prostate SABR as per PACE B trial can be clinically implemented in an off-trial, real world prostate cancer patient group with comparable acute toxicity rates. Work is on-gong to establish our longer term toxicity and efficacy data with further follow-up.

Keywords: prostate SABR SBRT

References:

1. NICE (2021) Prostate cancer: diagnosis and management. National Institute for Health and Care Excellence.

2. Brand et al. (2019) Intensity-modulated radiotherapy versus stereotactic body radiotherapy for prostate cancer (PACE-B): acute toxicity findings from an international, randomised, open-label, phase 3, non-inferiority trial. The Lancet. 20, (11) p1531-1543. https://doi.org/10.1016/S1470-2045(19)30569-8 3. Tree et al. (2022) Intensity-modulated radiotherapy versus stereotactic body radiotherapy for prostate cancer (PACE-B): 2 year toxicity results from an open label, randomised, phase 3, non-inferiority trial. The Lancet. 23 (10) p1308-1320. https://doi.org/10.1016/S1470-2045(22)00517-4

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Digital Poster

Dosimetric factors impacting urethral toxicity following stereotactic prostate radiotherapy