Study population and study setting
Patients are referred to University College London Hospitals (UCLH) trust for counselling regarding PCa treatment options. If surgery is their preferred choice and they meet the eligibility criteria, patients are invited to enrol in the study at their pre-surgical consultation. Study procedures and outcomes are explained and a patients receive a patient information sheet. Patients who agree sign the approved consent form. All patients who fulfil the inclusion criteria are invited to participate. Diagnosis of non-metastatic disease is based on the current standard diagnostic imaging methods including CT scans, multi-parametric magnetic resonance imaging (mpMRI), Bone Scan (BS) and/or PSMA-PET scan.
Eligibility criteria
Inclusion criteria:
- Patients with unfavourable intermediate, high- or very-high risk non-metastatic PCa based on the National Comprehensive Cancer Network (NCCN) guidelines.
- Scheduled for robot-assisted RP at UCLH.
- Patients who sign the informed consent form.
Exclusion criteria:
- Diagnosis of another synchronous cancer.
- Patients who had received previous PCa treatment.
- Patients who receive neo-adjuvant ADT.
Withdrawal criteria:
- Enrolled patients deemed unfit or unwilling to undergo RP.
- Failure to process the pre-op sample (technical issues).
- Withdrawal of consent to continue participating in the study.
Interventions
Radical Prostatectomy
After PCa diagnosis and staging, RP is performed using a minimally invasive approach with robot-assisted surgery as the standard of care in the National Health Service (NHS). RP involves the complete removal of the prostate and seminal vesicles with or without lymphadenectomy. Tissue-sparing approaches are guided by a pre-surgical mpMRI-based planning meeting.
CTC analysis
Twenty millilitres of peripheral blood is collected from each patient during the pre-and post-RP PSA test blood acquisition. Samples are taken to the laboratory at the Barts Cancer Institute (BCI), John Vane Science Centre, Charterhouse Square. We aim to process samples within 4 hrs of acquisition and the procedure is carried out as described previously (12). Briefly, the buffy-coat is isolated from 7mL whole blood, washed with phosphate buffered saline (PBS), and diluted in isolation buffer (PBS containing 1% bovine serum albumin and 2mM ethylenediaminetetraacetic acid (EDTA)). The cell solution is added back to the original vacutainer containing 0.5mL whole blood and placed into the Parsortix® system. The sample is passed through the Parsortix® microfluidics to a cassette where the cells are separated based on size and deformability. Harvested cells including CTCs are fixed with acetone on a microscope slide. Immunofluorescence analysis involves staining the slides for antibodies that target the leukocyte-specific marker CD45-Allophycocyanin (Miltenyi biotec cat no. 130-113-114), the epithelial marker Cytokeratin-Fluorescein Isothiocyanate (Miltenyi biotec cat no. 130-118-964), and the mesenchymal marker Vimentin-AlexaFluor 568 (abcam cat no. ab202504). Cellular DNA is identified using 4’,6-diamidino-2-phenylindole (DAPI). CTC slides are scanned on a Nanozoomer S60 fluorescence microscope (Hamatsu®) using a 20x objective. For the CTC RNA extraction, CTCs are harvested from the Parsortix® and added to 2x lysis buffer solution (Angle) in 1:1 ratio. The vial is vortexed and stored at -80°C prior to analysis. Remaining blood samples are separated into plasma and peripheral blood mononuclear cells and stored at -80°C in the Robert Lane Tissue Bank (RLTB) for further research use.
Participant timeline
Blood samples are taken for CTC analysis before surgery during routine pre-surgery testing. At routine 3-month post-surgery follow-up PSA testing, patients are invited to donate a second blood sample if they have not undergone additional treatments such as hormonal or radiation therapy. Clinical follow-up is carried out at 3, 6- and 12-months post-op and then on an annual basis. Medical records will be reviewed until the end of the project to ascertain whether subsequent PSA tests are positive, indicating BCR (PSA ≥ 0.2 ng/mL), imaging-proven metastasis, or if they have received salvage treatment with hormones/radiotherapy, PCa-specific mortality or other causes. Table 1 summarizes study assessments.
Table 1. Patient recruitment, sample collection and follow-up procedure
Procedure
|
Screening/ Baseline
|
Pre-RP
|
3 months post-op
|
6 months post-op
|
12 months post-op
|
Annual follow-up 2 to 10 years
|
Eligibility assessment
|
x
|
|
|
|
|
|
Informed Consent
|
x
|
|
|
|
|
|
Blood Sample collection
|
|
x
|
x
|
|
|
|
PSA
|
|
x
|
x
|
x
|
x
|
x
|
Medical record review and online app/phone follow-up; (PSA and/or Adjuvant therapies) rates of BCR, metastasis, other progression events and death
|
|
|
|
x
|
x
|
x
|
RP Radical Prostatectomy, BCR Biochemical recurrence. PSA Prostate specific antigen.
Outcome Measures
Primary outcome
The primary outcome is post-RP treatment failure. The primary analysis will occur after 4.5 years of follow up after the start of recruitment. Post-RP treatment failure is defined as a PSA ≥ 0.2ng/mL at routine PSA testing after RP. If patients have a rising PSA trajectory and clinicians recommend additional treatment before reaching the 0.2ng/mL threshold, this will also be considered a treatment failure. Additionally, any metastatic lesion detected by imaging tests independent of the PSA level will be considered a treatment failure. This combined post-RP treatment failure primary endpoint will maximise capture of all clinically significant cancer recurrence events.
Secondary outcomes
- BCR during the first 4.5 years of follow-up: PSA ≥ 0.2ng/mL at any time post-RP and remaining at this level or further increase afterwards without further treatment.
- Metastasis (any location)-free survival during the first 4.5 years of follow-up.
- Deaths from any cause during the first 4.5 years of follow-up.
- Prostate cancer-specific deaths during the first 4.5 years of follow-up.
- Metastasis (any location)-free survival at 10 years follow-up.
- Prostate cancer-specific survival at 10 years of follow-up.
- Overall survival at 10 years of follow-up.
Criteria for discontinuing or modifying allocated interventions.
Patients with positive surgical margins (PSM) or positive lymph nodes based on histopathological examination will be analysed separately. Patients can withdraw their consent at any time by sending an email or letter with their contact details to the address provided in their patient information sheet (PIS). If the donated samples have not already been used for research purposes, they will be removed from storage and destroyed, as well as any data that may have been collected and stored.
Relevant concomitant care permitted or prohibited during the trial and provisions for post-trial care
Patients are excluded from the trial analysis if they receive ADT before surgery as this may interfere with the accuracy of the CTC status. However, treatment decisions are not informed by the CTC results. All clinical staff and patients are blinded to CTC results. Therefore, standard of care treatment interventions will be decided by clinical care staff who are blinded to patient CTC status. Follow-up at 3 months is done at UCLH, subsequent follow up is done at their corresponding local hospitals or General Practitioner (GP) practice.
Blinding
To avoid influencing standard patient treatment, management, and progression outcomes after RP, the patients and all members of the clinical care team are blinded to the CTC results. Only the laboratory team is aware of the patients’ CTC status. The laboratory team are blinded to the patients’ clinical status, progression, and outcomes. There are no criteria for unblinding, as this is an observational study. The study findings will not affect patient care for the participants during the course or after the end of the study period.
Data management
Each patient is allocated a unique pseudo-anonymised ID used by the laboratory research team. This unique ID is recorded in the RLTB database for future correlation analysis of CTC results with clinical follow-up data. There will be fewer patients for post-RP than for pre-surgical blood collection based on patient exclusion criteria after RP. Completed consent forms are handed over to the RLTB for secure storage.
The data generated from this study includes immunofluorescence images of CTCs, RNA expression data of metastasis-associated genes in CTCs, and follow-up data on clinical and cancer progression associated with PCa patients. These data are also securely stored in a designated folder on the BCI IT server. The data is curated throughout its life cycle (during the study and before the data is published). Each digital PCR is performed using Angle® optimized method for multiplex CTC gene expression analysis. Gene expression value is recorded in the original data format and saved in the above-designated folder in the BCI server and will be available for data sharing after publication.
Statistical methods
In the reporting of this study, we will adhere to the STARD guidance (ref: https://www.equator-network.org/reporting-guidelines/stard/). The study flow and patient characteristics will be reported. Accuracy measures will be presented along with 95% confidence intervals (CIs). The primary analysis will focus on estimating the accuracy of pre-surgery CTC score positivity in detecting post-RP treatment failure, as defined above. We will report the observed specificity, positive predictive values, and negative predictive values. Furthermore, specificity will be presented over time. To address the potential artificial inflation of false positives due to increasing prevalence over time, additional analyses will be conducted. These analyses will be repeated for the CTC test, which combines CTC score positivity with CTC gene-expression analysis.
Recurrence events and follow-up CTC results will be reported and compared over time. BCR-free survival will be estimated, and Kaplan-Meier curves will be presented and stratified by CTC test result. Likewise, metastases-free, prostate cancer and overall survival will be reported and stratified by CTC test result. CTC data will be explored along with other pre-operative risk factors using multivariate analysis. No interim analysis is planned. A subgroup analysis will be performed to analyse the predictive value of pre-surgery CTCs in patients with positive surgical margins (PSM), lymph node metastasis, or those who received adjuvant treatment.
Consideration with respect to missing data
The primary analysis is concerned with measures of accuracy and only data which has known positive or negative values will be included. The study flow diagram will aid interpretation and show the number of participants recruited who did not provide study samples. The number of samples collected, analysed and providing data contributing to these accuracy measures will be reported.
Kaplan-Meier curves will be reported with the numbers at risk over time. All eligible participants providing valid, blood samples which are analysable using the CTC tests will be included in analyses. Time to event will be from date of blood sample was taken up to the point an event occurs, or death, loss to follow up, withdrawal, or the analysis cut-off date, whichever occurs first. Data from those not experiencing an event will be right censored. Reasons for loss to follow up or withdrawal will be collected where possible and monitored by the TSC. Non-informative censoring will be used in this study where the patient and clinical team are blinded from the CTC test result and where the CTC result is not used to influence care and therefore drop out.
Multivariable regression/analyses will be on a complete case basis, with numbers included in the analysis report.
Sample size
Consistent with previous work, this study estimates that CTCs can predict post-RP cancer events with 95% sensitivity. During the first 4.5 years of follow-up, the hypothesised prevalence of BCR events in high-risk PCa is at least 40%. To confirm an expected sensitivity of 95% within 5% precision on either side of a 95% confidence interval (CI) in a sample with an underlying prevalence of 40% requires at least 73 events, that is at least 183 recruited individuals. We inflated this by 8.5% to target a recruitment of 200 participants to ensure the suitability of samples and measurable outcomes.
We expect to screen approximately 490 patients over 2 years and recruit 294 patients to compensate for the 20% PSM and 15% adjuvant therapy rates in patients undergoing surgery. This will allow us to evaluate 200 post-surgery CTC samples. Specificity is important considering the future circumstance of potentially denying curative surgery if a CTC test falsely indicates metastasis. A study size of 200, including 120 true negatives, would provide a 97.5% lower confidence limit with a specificity of 99% (1% false positive rate). However, we anticipate that the specificity will be lower due to positive results for those who experience recurrence beyond the 5-year study period. Assuming that these events are due to micro-metastasis at the time of surgery, observed sensitivity and specificity will be used, plus additional analyses assuming that up to 20% of the events occur after the funded 5-year project to estimate the real false positive and negative rates.
Plans to give access to the full protocol, participant level data and statistical code
When the relevant safeguards have been applied for intellectual property and we have published the main findings, anonymised data of the findings will be publicly accessible. The research data on the main outcomes will be made available as a spreadsheet through a web link published in scientific journals and/or the BCI Institute’s website.
Oversight and monitoring
The study’s management group (SMG), consisting of the PIs/Co-Is, key collaborators, lab team members and statistician convenes every month. The Trial Steering Committee (TSC), which includes a patient member, a consultant urologist (chair), a biomarker study specialist/statistician, and a basic research scientist independent from the study, monitors recruitment and study progress in terms of outcome data collection and statistical assumptions underpinning the study, including a confidential review of the event rates. The TSC meets on an annual basis. Due to the observational nature of the study, there is not a separate data monitoring committee.
Adverse event reporting and harms
Obtaining blood samples for this study includes the risks associated with venepuncture, such as temporary discomfort and bruising. Blood samples for pre-operative preparation and pre-and post-operative PSA monitoring are part of the NHS standard of care for PCa patients; therefore, obtaining samples for this study does not involve any additional risk or burden for patients.
Frequency and plans for auditing trial conduct
The Sponsor, funding body, and/or regulatory bodies may audit the study site or central facility. The PI will ensure an adequate quality and number of monitoring activities conducted by the study team. This will include adherence to the protocol, consenting procedures, and source data verification to ensure adequate data quality. The relevant PIs will inform the sponsor (Queen Mary University of London) should they have concerns which have arisen from monitoring activities, and/or if there are problems with any oversight or monitoring procedures. RLTB will be auditing consent forms on receipt, and study auditing will be carried out as per the local RLTB policy with prior agreement with the study team.