Hemi-Ablative Prostate Brachytherapy

This is a pilot Stage IIS study to evaluate the feasibility of performing a larger multicentre trial.The HAPpy study is a prospective development study offering hemi ablative LDR brachytherapy to 34 men with histologically proven low or intermediate risk localised prostate adenocarcinoma which affects a single lobe of the prostate.The data obtained from these 34 patients will be compared to matched patients from a retrospective cohort of whole gland brachytherapy patients treated in the same institution.Precise mapping and characterisation of the disease will be established using mp-MRI (T2-weighted and DCE(gadolinium)) imaging and transperineal template biopsy (TTB). Only the lobes with disease (left or right half of the gland) will be treated provided that the contralateral side is free of disease. Patients will be followed for two years post treatment at which time a further mp-MRI and TTB will confirm disease control outcomes.

Focal therapy for prostate cancer is a new idea and is considered an experimental treatment which needs to be evaluated within carefully conducted clinical trials . Rather than investigating focal therapy in a strict sense where only known areas of disease are treated, a more conservative approach needs to be taken until more information can be obtained regarding the outcomes of changing treatment techniques. Hemi-ablative focal therapy is considered to be a low-risk treatment and investigations into the performance of the technique should provide a pathway for future investigations of less conservative methodologies. Hemi-ablative focal therapy treats half of the prostate gland with a treatment margin, effectively treating at least 50% of the whole gland with a prescription dose. In theory, this should lessen the side effects associated with radical treatment while still maintaining disease control.This type of treatment is only suitable for patients with unilateral disease.

An international group of experts was established to form a consensus on how to design and conduct an LDR focal brachytherapy program for clinical trials. The group's findings were published by Langley et al and a dosimetric modelling study by Al Qaisieh et al.

Focal hemi gland brachytherapy will be delivered by means of an adaptation of same real-time planning technique (denominated 4D Brachytherapy) used to deliver whole gland LDR prostate brachytherapy. Stranded iodine 125 sources are implanted on the periphery of the prostate gland and loose iodine 125 sources are implanted within the central volume of the gland. Because all planning and dosimetry are done in real-time, radiotherapy physics will be able to adhere to the strict planning protocols required for this study.

Treatment planning: For standard whole-gland treatment, the whole prostate gland is delineated to form the Planning Target Volume (PTV) and the V100 is planned such that it covers the entire PTV plus a 0.5cm margin. For hemi-ablative focal treatments, the prostate will be divided into half and a new HTV (called the HemiTreatment Volume) is outlined on the side of the prostate determined to have clinically significant disease. A treatment margin of 0.5cm is considered around the HTV, which is similar when planning whole-gland treatment. In this way, >95% of the HTV is aimed to receive 100% of the prescription dose (V100). The V150 is situated in a semi-horseshoe shape in order to spare the urethra from high doses of radiation.

Dose parameters to critical organs are as follows:-

HEMI PROSTATE:

Prescription Dose 145Gy V100 = >95% V150 = 50-60% D90 = 140 - 160 Gy

URETHRA:

V150 <15%

RECTUM:

D0.1cc <200 Gy

The trial design follows recommendations published by the Balliol Collaboration under the Idea, Development, Exploration, Assessment, Long-term follow-up (IDEAL) model for a surgical study.

Data Collection and Statistics

1. Sample Size- Pilot Study There are no published results available and this technique has not been trialed to determine its effectiveness in disease control and quality of life outcomes. As such, a preliminary study is necessary to determine efficacy and feasibility before a large, multi-centre trial can be performed where a significant number of patients can be recruited for appropriate statistical analysis. The trial site currently treats ~300 patients per year for whole-gland brachytherapy. Of these 300 patients, ~25% present with unilateral disease that is low and intermediate risk. Recruitment will be over 18 months, in which time 100 patients should be eligible for the HAPpy trial. We anticipate a 25% drop-out rate after mp- MRI and template prostate mapping (TPM) biopsy results and a further 25% drop-out due to refusal to participate. This means that ~50 patients should be available for recruitment into the study over an 18 month period. In order to assess a decrease in side-effects (based on quality of life (QoL)) data of at least 10%, 34 patients will be required for the study. This is comparing two independent groups (prospective hemi group versus retrospective whole-gland group) when using α = 5%, β = 10%, and σ = 20%.
2. Data collection The main research co-ordinator is a qualified and experienced data manager. Data will be collected in both paper and electronic form and the data will be stored in one place and backed up twice on two different servers. Data will be held according to the Data Protection Act 1998 and pseudo anonymised as necessary. Each participant will be given a study number and this will be used on all of their study records. The patient number will be known to the chief investigator, the research co-ordinator, and the research radiographer or nurse assigned to the study. Data will be kept in a secure manner in the research offices with access to named individuals from the study group only. The paper records will be kept for a minimum of 10 years after the end of the study. A research radiographer or nurse will be appointed at the time of trial commencement to ensure that the Quality of Life (QOL) questionnaires are completed at each follow-up visit as required by the trial protocol. The research radiographer or nurse is also responsible for ensuring that each patient in the trial has appropriate appointments set up for each treatment, scanning (mp-MRI, biopsy), and follow-up visit and the necessary information is collected at each visit under the protocol. All clinic visit information including questionnaires, scans, biopsy results, and blood results will be kept in study records.
3. Analysis Thirty-four patients will be examined in the HAPpy trial and with this small sample number, non-parametric analysis of the data will be the most suitable. Patients will be paired or matched according to their tumour staging and pathology, age, and baseline scores. The Mann-Whitney U test, the Wilcoxon test, as well as tests for normality (if appropriate) of the data will be performed to determine if there are differences in the trial groups. Analysis of variance will be performed if the data is appropriate to use in this manner. Data to be collected:- IPSS + QoL questionnaire = Numerical scores, time-points IIEF-5 QoL questionnaire = Numerical scores, time-points EORTC-QLQ-PR25 bowel symptoms questionnaire = Numerical scores, time-points Dosimetry Values for PTV and HTV = Numerical V100, V150, D90 = Numerical Dose to the Urethra (V150) = Numerical Dose to the Rectum (D0.1cc) = Numerical Pathology review of biopsies (all) Standard reporting, qualitative, ranked mm of core invaded = Numerical Biopsy % core invaded = Numerical Prostate-specific antigen (PSA) = Numerical, time-points EN2 = Numerical, time-points Gleason Score= Numerical Staging = Standard reporting, qualitative, ranked Outcomes will be reported as estimates with 95% confidence intervals using appropriate methods based on the type of data. For patient reported outcomes with available baseline measurements, a comparison will be made with baseline values using paired analyses. Logistic regression will be used to investigate associations with potential risk factors for histological failure, considering PSA and EN2, Gleason score, cancer core length involvement (mm and %), number and % of positive biopsies for any cancer on TTB, stage and risk group. Sensitivity and specificity (with 95% confidence intervals) will be estimated in considering the use of standard PSA kinetics and thresholds for identifying clinically significant cancer. Scores from the quality of life questionnaires will be used in multivariable cross-sectional and longitudinal regression analysis comparing the treatment groups. Dosimetric evaluation to the PTV, HTV, and structures (urethra, rectum,bladder) will be performed (ultrasound real-time planning and post-operative CT). The dosimetry will be correlated with QoL information and disease control outcomes. Results from the TTB will be compared with the mp-MRI scans to evaluate the efficacy of using mp-MRI for diagnosis of disease. Disease modelling in three dimensions may be performed if a suitable physicist can be found to perform such an analysis. EN2 and PSA evaluation over time will be examined using regression analysis and compared between the two trial arms. Biopsy and mp-MRI results at 2-years (disease control outcomes) will be compared with pre-treatment biopsy and mp-MRI data and correlated with QoL information and dosimetry. Thirty-four patients will be examined in the HAPpy trial and with this small sample number, non-parametric analysis of the data will be the most suitable. Patients will be paired or matched according to their tumour staging and pathology, age, and baseline scores. The Mann-Whitney U test, the Wilcoxon test, as well as tests for normality (if appropriate) of the data will be performed on the data to determine if there are differences in the trial groups. Analysis of variance will be performed if the data is appropriate to use in this manner.
4. Reporting of Results The data will be analysed and submitted for peer reviewed journals for publication as full manuscripts. Abstracts to conferences will also be submitted for poster or oral presentation. An interim analysis at 12 months using histological and imaging data will be performed once sufficient data are available.

Data collection and reporting of results will follow the guidelines outlined in CONSORT and STROBE for clinical trials.