Trial Information

Trans-Rectal Placement of Prostatic Fiducial Markers Under MR-Guidance in Patients Receiving External Beam Radiotherapy for Prostate Cancer: A Pilot Study

Effective image-guided prostate therapies require excellent visualization of the prostate
and surrounding anatomy, such that cancerous tissue can be treated while avoiding nearby
neural and vascular structures. As such, Magnetic Resonance Imaging is well suited for
image-guidance because of its excellent soft tissue contrast, multiplanar capabilities, and
the potential to yield spectral/biological tumor mapping. Despite the potential for
MRI-guided prostate therapies, there are currently no techniques that allow for precise
trans-rectal intraprostatic needle placement in patients.

In this pilot study we seek to validate the accuracy and tolerability of a new system and
technique that allows for accurate placement of needles within the prostate based upon MR
images. The method is very similar to transrectal ultrasound guided biopsy of the prostate,
except that it is applicable within a closed high-field MRI scanner. Four gold fiducial
markers will be placed within the prostate under needle guidance in a series of patients
with localized prostate cancer before external beam radiotherapy. Fifteen patients will be
enrolled onto this study with sample size determined to obtain reasonably precise estimates
of mean placement accuracy. The accrual period is expected to be less than a year.

While placement of the fiducial markers has no direct therapeutic benefit for the patient,
intraprostatic radiopaque fiducial markers (placed under ultrasound) have shown value in
assessing daily setup errors and off-line organ motion during external beam radiation
therapy for prostate cancer. Therefore, a secondary objective is to gain experience using
these intraprostatic fiducial markers for daily assessment and adjustment of external
radiation beam targeting. These markers can also be utilized to aid in CT-MRI fusion and
results in better target delineation for treatment planning. In this way, prostate cancer
patients who are receiving external-beam radiation therapy may benefit from participation.