PINPOINT Feasibility Study V0.11
Research type
Research Study
Full title
Pioneering Imaging techniques for optimising dose delivery in Post-Operative prostate radiotherapy. A feasibility study.
IRAS ID
290569
Contact name
Julia Murray
Contact email
Sponsor organisation
The Royal Marsden NHS Foundation Trust
Duration of Study in the UK
1 years, 0 months, 0 days
Research summary
Summary of Research
Approximately 47,000 men are diagnosed with prostate cancer yearly in the UK, 15% of which receive surgery (radical prostatectomy) as primary treatment. Of these men one third develop recurrence after prostatectomy and are offered post-operative radiotherapy.Radiotherapy is targeted at the area where the prostate used to be, this includes potential relapse sites (PRS); vesicourethral anastomosis, bladder neck and retrovesicle space. When planning post-operative radiotherapy, the lack of a visible target means surrounding normal tissue is used to guide clinical target volume (CTV) delineation. The CTV is the area of tissue to be treated to the full radiotherapy prescription and includes PRS. Typically, the CTV is defined on a radiotherapy planning computer tomography (CT) scan.
The CTV lies adjacent to the bladder and rectum and is highly susceptible to positional changes influenced by organ filling. To identify and correct for CTV displacement during daily radiotherapy a cone-beam CT (CBCT) is acquired, this is an image similar to a CT scan but taken immediately prior to treatment delivery.
CT visualisation of PRS has been reported as inadequate, increasing the risk of missing or miss-identifying CTV structures during radiotherapy planning and delivery. To compensate for restricted visualisation on CT and CBCT an additional 1cm circumference around the CTV is treated to the prescription dose, this volume is referred to as the planning target volume (PTV). This margin reduces the risk of missing the target however its inclusion of normal tissue increases the risk of patient toxicity.
We propose that visualisation of PRS and surrounding normal tissue structures is enhanced on magnetic resonance imaging (MRI) compared to CT and on transperineal ultrasound (TPUS) compared to CBCT. This project investigates the reality of this statement by quantifying the confidence and reliability with which anatomical structures can be identified and delineated on all four image types.
Summary of Results
This study set out to investigate the feasibility of using magnetic resonance imaging (MRI) and transperineal ultrasound (TPUS) to visualise normal anatomy and potential sites of relapse in patients having post-operative prostate cancer radiotherapy. It aimed to determine whether potential relapse sites and surrounding normal tissue structures could be visualised more frequently and reliably on MRI compared to current standard radiotherapy imaging. Current standard radiotherapy imaging includes a computer tomography (CT) scan, used to map where the treatment needs to be directed, and cone-beam CT (CBCT) images, taken just before radiation, used to ensure the patient is in the correct position for treatment.
The project failed to recruit the sample size needed to assess the feasibility of using MRI and TPUS to visualise normal anatomy and potential sites of relapse in this patient group. Only two of the required 14 patients were recruited. Both participants had an MRI image at radiotherapy planning, participant one did not have a TPUS scan at radiotherapy planning due to system failure, the second participant did have TPUS imaging at the planning stages. Both participants had two TPUS scans during radiotherapy as per the protocol. Acquisition of these additional scans did not alter the treatment of the patient in any way.
Failure to recruit was the result of various factors; firstly, the project was initially delayed due to covid, staff moved on, reducing technical support for the study. Secondly, once open, recruitment was delayed due to technical issues with the TPUS machine, meaning it could not be used. Finally, the radiotherapy treatment unit connected to the TPUS system was removed from service, leaving us without an integrated system. The manufacturer of the TPUS system also stopped making the device. These factors left us no choice but to close the study.Research images were anonymised and uploaded by the trial team into a secure password protected and monitored programme. However, as data was so limited, no formal analysis of the images was conducted. This means we cannot comment on the ability of MRI and TPUS to visualise normal anatomy and potential sites of relapse in patients having post-operative prostate cancer radiotherapy.
REC name
London - Chelsea Research Ethics Committee
REC reference
21/LO/0277
Date of REC Opinion
25 Jun 2021
REC opinion
Further Information Favourable Opinion