The purpose of this research is to investigate whether stereotactic body radiotherapy (SBRT), precise X-ray treatment, is best given in five treatments (also called fractions) over 10 days or in two treatments over 8 days. SBRT is an accurate way to deliver a high dose of radiotherapy to the prostate in a smaller number of doses. We have considerable experience with 5-dose SBRT and now wish to examine the feasibility and safety of delivering treatment over two, larger, doses. Previous work has shown it is theoretically possible to deliver two fraction SBRT on the MR-linac and previous studies have shown internal radiotherapy (brachytherapy) administered in two fractions to be a safe option for patients with low-risk prostate cancer.
All treatment within this trial will be delivered on a new, state of the art, radiotherapy machine called an MR-linac (Magnetic Resonance Linear Accelerator). It puts together an MRI scanner with a radiotherapy treatment machine called a Linear Accelerator. The use of the MR-linac means there is no extra radiation dose given when taking images (unlike computerized tomography (CT) scans or X-ray), enabling us to adapt the radiotherapy plan each day if needed to more precisely target the prostate. The results of the study will enable us to find out if the new, shorter treatment (2 doses of radiotherapy), has a similar level of side effects as the 5 dose treatment and is suitable for further study.
Men aged ≥18 years
Histological confirmation of prostate adenocarcinoma requiring radical radiotherapy
Gleason score 3+4 or 4+3 (Grade groups 2 or 3)
MRI stage T3a or less
Contraindications to MRI (e.g. pacemaker, potentially mobile metal implant, claustrophobia)
International Prostate Symptom Score (IPSS) 13 or higher
Post-void residual >100 mls
Prostate volume >80cc
Parallel
SBRT
RadiationStereotactic Body Radiotherapy. Ultrahypofractionated radiotherapy.
Genitourinary (GU) toxicity
The proportion of patients experiencing CTCAE (Common Terminology Criteria for Adverse Events) Grade 2+ genitourinary (GU) toxicity from the start of radiotherapy up to 12 weeks post-treatment.
Physician-reported CTCAE Genitourinary (GU) and Gastrointestinal (GI) toxicity
Physician-reported CTCAE GU and GI toxicity will be reported during treatment and at 12 weeks post-treatment will be summarised according to grade and treatment received using descriptive statistics at each time point.
Physician-reported CTCAE Genitourinary (GU) and Gastrointestinal (GI) late toxicity
Late toxicity (CTCAE) at 1, 2 and 5 years post-treatment will be summarised according to grade and treatment received at each time point.
Quality of life patient-reported outcomes
Combined data from the IPSS (International Prostate Symptom Score), EPIC-26 (Expanded Prostate Index Composite-26), EQ-5D (EuroQol-5D) and IIEF-5 (International Index of Erectile Function) QOL instruments will be summarised. Domain scores from the quality of life patient-reported outcome tools will be derived using standard algorithms with missing data handled accordingly. Domain scores and individual items from the patient questionnaires will be presented graphically at each time point and summarised using descriptive statistics, separately for each treatment group. Changes from baseline will be assessed within treatment groups, and multiple regression models (e.g. ANCOVA, ordinal logistic regression or longitudinal models) will investigate patient and clinical factors that may be associated with change in patient-reported outcomes.
PSA (Prostate Specific Antigen) control and biochemical failure/progression
Time to event.
Assess bi-parametric MRI prostate imaging parameters during treatment
Descriptive statistics will be used to report and analyse the change in ADC (Apparent diffusion coefficient) between baseline and 4 weeks and between baseline and 12 weeks.
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