Stereotactic radiotherapy with focal boost for intermediate and high-risk prostate cancer: Initial results of the SPARC trial

Luke Nicholls; Yae-Eun Suh; Ewan Chapman; Daniel Henderson; Caroline Jones; Kirsty Morrison; Aslam Sohaib; Helen Taylor; Alison Tree; Nicholas van As

doi:10.1016/j.ctro.2020.10.004

Stereotactic radiotherapy with focal boost for intermediate and high-risk prostate cancer: Initial results of the SPARC trial

Clin Transl Radiat Oncol. 2020 Oct 20:25:88-93. doi: 10.1016/j.ctro.2020.10.004. eCollection 2020 Nov.

Authors

Luke Nicholls^{1

2}, Yae-Eun Suh¹, Ewan Chapman^{1

3}, Daniel Henderson⁴, Caroline Jones¹, Kirsty Morrison¹, Aslam Sohaib¹, Helen Taylor¹, Alison Tree^{1

3}, Nicholas van As^{1

3}

Affiliations

¹ Royal Marsden NHS Foundation Trust, 203 Fulham Road, London SW3 6JJ, UK.
² School of Medicine, University of Queensland, Brisbane, Australia.
³ The Institute of Cancer Research, 237 Fulham Road, Chelsea, London SW3 6JJ, UK.
⁴ University Hospitals Birmingham NHS Foundation Trust, Mindelsohn Way, Edgbaston, Birmingham, West Midlands B15 2GW, UK.

Abstract

Introduction: Dose escalation to dominant intraprostatic lesions (DILs) is a novel method to increase the therapeutic ratio in localised prostate cancer. The Stereotactic Prostate Augmented Radiotherapy with Cyberknife (SPARC) trial was designed to determine the feasibility of a focal boost defined with multiparametric magnetic resonance imaging (mpMRI) using stereotactic ablative body radiotherapy (SABR).

Materials and methods: Patients were included with newly diagnosed intermediate to high risk prostate cancer with at least one of: Gleason score 4 + 3, stage T3a, or PSA > 20 ng/ml. Visible disease on mpMRI was mandatory and up to 2 separate nodules were allowed. All patients received androgen deprivation. Patients received 36.25 Gy in 5 fractions using CyberKnife® and the DIL received a simultaneous boost to a maximum of 47.5 Gy, as allowed by OAR constraints. Genitourinary (GU) and gastrointestinal (GI) toxicity was reported using the RTOG scoring criteria. International Index of Erectile Function (IIEF) and EQ-5D global health scores were regularly captured.

Results: An interim safety analysis was performed on the first 8 patients, recruited between July 2013 and December 2015. Median follow up was 56 months (range 50-74). Median D95 values for the prostate PTV and boost volume were 36.55 Gy (range 35.87-36.99) and 46.62 Gy (range 44.85-48.25) respectively. Of the dose constraints, 10/80 were not achieved but all were minor dose variations. Grade 2+ acute GU and GI toxicities were 37.5% respectively while grade 2+ late GU and GI toxicities were 12.5% and 0% respectively. IIEF and quality of life scores recovered over time and all patients remain in biochemical remission.

Conclusion: The first patients have been successfully treated with prostate SABR and focal boost on the SPARC trial, with excellent adherence to the planning protocol. Toxicity and efficacy results are promising and further recruitment is underway.

Keywords: Intermediate- and high-risk; Prostate cancer; Radiotherapy; Stereotactic ablative body radiotherapy.

Grants and funding

28284/CRUK_/Cancer Research UK/United Kingdom