ESTRO 2024 - Abstract Book

S2337

Clinical - Urology

ESTRO 2024

491

Proffered Paper

SBRT Focal Boost for Localised Prostate Cancer: Primary Outcomes of the SPARC Prospective Trial

Binnaz Yasar 1,2 , Yae-Eun Suh 1 , Ewan Chapman 3 , Luke Nicholls 4 , Daniel Henderson 5 , Caroline Jones 6 , Kirsty Morrison 7 , Emma Wells 1 , Julia Henderson 1 , Carole Meehan 1 , Aslam Sohaib 1 , Helen Taylor 1 , Alison Tree 1,2 , Nicholas Van As 1,2 1 Royal Marsden NHS Foundation Trust, Urology Unit, London, United Kingdom. 2 The Institute of Cancer Research, Urology Research, London, United Kingdom. 3 St Bartholomew’s Hospital, Radiotherapy department, London, United Kingdom. 4 University of Queensland, School of Medicine, Brisbane, Australia. 5 University Hospitals Birmingham NHS Foundation Trust, Radiotherapy department, Birmingham, United Kingdom. 6 Leeds Teaching Hospitals NHS Trust, Physics department, London, United Kingdom. 7 Guy's and St Thomas' NHS Foundation Trust, Radiotherapy department, London, United Kingdom

Purpose/Objective:

Dose escalated radiotherapy is associated with better outcomes at the expense of increased toxicity.[1] Stereotactic radiotherapy with dose escalation to the dominant intraprostatic lesion (DIL) is one logical approach to improve disease control in high-risk disease whilst limiting toxicity. In this prospective phase 2 trial, we evaluated the toxicity and quality of life outcomes in participants treated with CyberKnife based stereotactic body radiotherapy (SBRT) with simultaneous integrated boost to the MRI defined DIL in localised prostate cancer.

Material/Methods:

SPARC is a single institution phase II prospective trial that was approved by the local Research Ethics Committee (Clinical Trials.gov ID: NCT02145494). Eligible participants were men with newly diagnosed, biopsy-proven localised prostate cancer with unfavourable intermediate to high-risk features with up to two MRI identified DILs. Participants had at least one of the following: Gleason 4+3 or above, MRI defined T3a N0, PSA greater than 20 ng per millilitre. SBRT was prescribed to 36.25Gy to the prostate delivered on alternative days with a simultaneous boost to DIL up to 47.5Gy as allowed by organs at risk (OAR) constraints delivered by CyberKnife. All participants received androgen deprivation therapy. The primary outcome measure was acute grade 2 and above genitourinary (GU) toxicity. Acute and late GU and gastrointestinal (GI) toxicity using RTOG scoring, biochemical parameters, IPSS, IIEF5, EQ5D quality of life outcomes were assessed at end of treatment (last fraction for SBRT), 2 weeks, 4 weeks and 12 weeks following treatment, then every 3 months for the first 2 years, every 6months from year 2 to 5, and annually thereafter for 10 years.

Results:

Between July 2013 and March 2023, 20 participants were enrolled on the study with a median follow-up of 30 months. The median D95 dose to DIL was 47.43Gy. Cumulative acute grade 2 and above genitourinary (GU) and gastrointestinal (GI) toxicity was 25% and 30%, respectively. One patient developed acute grade 3 GU toxicity (5%). By week 12 post treatment, all grade 2 or above GU and GI toxicity had resolved. There is no late grade 3 GU or GI