A Phase II Study of MR-Guided High Dose Rate Brachytherapy Boosts For Prostate Cancer
Brachytherapy, the placement of a radioactive source close to a tumor, is rapidly becoming
an important modality for patients with prostate cancer because higher and more conformal
doses can be safely delivered compared with external beam radiotherapy.
High dose rate (HDR) temporary implants offer several treatment and research based
advantages over permanent seeds, including exceptionally complex and accurate dosimetry in
reference to anatomic images.
Needle placement in brachytherapy procedures requires detailed image guidance, traditionally
obtained with trans-rectal ultrasound (TRUS). MRI offers a 3D dataset, arbitrary imaging
planes, and unparalleled soft tissue resolution of the anatomy, making it the modality of
choice for imaging the prostate gland.
A real-time MR-guided prostate permanent seed implant technique that utilizes both real-time
MRI and real-time dosimetry has been designed, implemented and reported. Results confirm
that TRUS-guided implants may be improved upon by using MRI. To our knowledge, HDR implants
have not yet been performed under MR guidance in a closed bore magnet.
The primary objective is to determine the quality of prostate HDR brachytherapy implants
performed under MR-guidance.
Quality is defined by the percentage of the planning target volume (PTV) encompassed by a
given percentage of the prescribed dose. In this study an implant will be of "acceptable"
quality if 80% of the PTV is encompassed by the 100% isodose (V100 greater than or equal to
80%), in accordance with RTOG guidelines.
Pathologically confirmed prostate cancer with the following features:
- Gleason score greater than 6, or greater than T2a, or
- PSA greater than or equal to 10, and no evidence of bone metastases;
Age greater than or equal to 18 years;
ECOG performance status of 0 or 1
The study is designed with a "run-in" pilot phase with the objective of refining the
The evaluation phase is a two-stage optimal design to evaluate the quality of the implant
with an early look for futility.
This study has the potential to enroll a maximum of 27 patients.
Radiation treatment parameters will be patterned after established guidelines in the
literature such as those reported by the American Brachytherapy Society and the
William-Beaumont Hospital. There will be no attempted dose escalation or attempts to
prescribe the dose to unconventional target volumes in this phase of the project.
Primary Purpose: Treatment
Kevin A Camphausen, M.D.
National Cancer Institute (NCI)
United States: Federal Government
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