In Vivo Dosimetry During Prostate Cancer Radiotherapy

As a part of your standard of care, you will have external beam radiation therapy. You will
have a computerized tomography (CT) scan of the pelvis before the external beam radiation
therapy.

For the CT scan, you will be given an enema to empty your bowel, and you will drink about 16
to 24 ounces of water to fill your bladder

A rectal balloon will then be inserted into your rectum and filled with either air or water.
You will then have the CT scan. The CT scan should take about 45 minutes.

If you agree to take part in this study, very thin (millimeter-sized) radiation detectors
will be attached to the rectal balloon during each of two CT scans per week you will have
while you are receiving radiation. You may have additional CT scans (without the detector)
each week if your doctor thinks it is needed.

The doses read by the radiation detectors will be compared to the doses that you were
originally scheduled to receive after each radiation treatment and at the end of the study.

You will be off study after your final radiation treatment using the rectal balloon.

This is an investigational study. Up to 15 patients will take part in this study. All will
be enrolled at MD Anderson.

Inclusion Criteria:

1. Any patients with prostate cancer who are undergoing routine radiation therapy for
their prostate cancer, including post-prostatectomy patients.

2. The selection criteria will be limited to the patient's ability to withstand
insertion of a rectal balloon and his willingness to participate in the study.

3. We will choose patients undergoing photon and proton treatments.

Exclusion Criteria: