High Dose Rate Prostate Brachytherapy: Dose Escalation to Dominant Intra-prostatic Nodule (Dosepainting)
This study will investigate the feasibility of using technology of ultrasound guided HDR brachytherapy to focally increase dose to regions within the prostate that are heavily infiltrated with cancer. Such regions, referred to as dominant intraprostatic lesions (DIL) can be visualized using diffusion contrast enhanced MRI employing an endo-rectal coil. The magnetic resonance (MR) images can be fused with the planning transrectal ultrasound (TRUS) prior to the brachytherapy procedure to design a dose distribution that will encompass the malignant volume with higher than the prescription dose. By its nature, brachytherapy has subvolumes that receive (for example)125% of the prescription dose or 150% of the prescription dose. With TRUS-guided and TRUS-planned HDR these areas can be manipulated to coincide with the DIL. The limit of dose escalation has been reached at whole prostate external beam doses of 81-86 Gy and still failure rates for intermediate and high risk disease are unacceptable. There is much interest in focal dose escalation and TRUS-guided HDR brachytherapy is perfectly suited to achieving this.
|Study Design:||Endpoint Classification: Safety/Efficacy Study
Intervention Model: Single Group Assignment
Masking: Open Label
Primary Purpose: Treatment
|Official Title:||High Dose Rate Prostate (HDR) Brachytherapy Dose Escalation to Dominant Intra-prostatic Nodule for Patients With Intermediate and High Risk Prostate Cancer|
- Feasibility of delivery of a higher than prescription dose to the dominant intra-prostatic nodule as defined on diffusion contrast-enhanced endo-rectal MRI, while respecting tolerance doses of adjacent normal organs. [ Time Frame: 12 months ] [ Designated as safety issue: No ]
Data to be collected are:
i) ratio of volume of gross tumour volume (GTV) to prostate volume ii) number of DIL's per prostate iii) isodose encompassing DIL without exceeding critical organ dose constraints (Urethral volume receiving 115%= 0, Dose to 1cc of rectal wall < 7 Gy)
- Acute toxicity compared to a cohort of 25 patients treated to standard dose [ Time Frame: 24 months ] [ Designated as safety issue: Yes ]
Data to be collected are:
i) urinary retention rate and duration ii) maximum International Prostate Symptom Score and time to normalize iii) rectal toxicity
- Efficacy will be assessed by repeat DCE MRI at 12 months and TRUS-guided prostate biopsy at 30 months. [ Time Frame: 30 months ] [ Designated as safety issue: No ]Repeat DCE endorectal MRI will be repeated at one year post treatment to assess imaging response. Histologic response will be assessed at 30 months as studies have shown that this is the optimal time for post radiotherapy prostate biopsy.
|Study Start Date:||May 2012|
|Estimated Study Completion Date:||December 2015|
|Primary Completion Date:||December 2013 (Final data collection date for primary outcome measure)|
Experimental: HDR interstitial brachytherapy
HDR prostate brachytherapy with dose escalation to 1250 cGy to the MRI-defined dominant intraprostatic lesion
Radiation: HDR interstitial brachytherapy
2 treatments of 1000 cGy will be delivered to the entire prostate volume while escalating the dose to the visible disease to 1250 cGy
Other Name: Planning soft ware Varian Medical Systems Vitesse III
Methods: If a dominant nodule is visualized on dynamic contrast enhanced (DCE) MRI, it will be contoured in 3D and the images fused to the planning TRUS study that is done in preparation for brachytherapy (of any type: seeds or HDR). The patient's treatment will consist of the standard combined external beam (4600 centiGray (cGy) in 23 fractions) and HDR brachytherapy boost (2 fractions of 1000 cGy given on days 5 and 15 of the external beam course). During each HDR treatment the plan will be manipulated such that the normally occurring high dose regions (125%, 150%) are positioned at the site of the identified disease. Normally approximately 60% of the prostate volume receives 125% of the dose and 30% receives 150%. By ensuring that the inherent dosimetry favors treatment of the known cancer, no region of the prostate would be "underdosed". HDR treatments are performed under general anesthesia as an out patient procedure.
Statistical Analysis: This is a feasibility study and the data reported will be descriptive including the frequency with which the DIL can be visualized in this population, the DIL volume compared to total prostate volume, and the isodose that can encompass the DIL without violating dose constraints to adjacent organs (urethra and bladder). Toxicity will be monitored and efficacy will be assessed by repeat DCE MRI at 12 months and biopsy at 30 months.
Please refer to this study by its ClinicalTrials.gov identifier: NCT01605097
|Canada, British Columbia|
|Cancer Center for the Southern Interior|
|Kelowna, British Columbia, Canada, V1Y5L3|
|Principal Investigator:||Matthew Schmid, MSc||Medical Physicst|