There are several different treatment schedules being used across the world for treatment of prostate cancer with radiation therapy. In order to determine the best radiation treatment for this disease, a study is being performed by the doctors at the Princess Margaret Hospital. This study will try to measure the effectiveness and side effects of an increased dose of radiation to the prostate that is also given over a shorter number of weeks than is usually done. In order to try to reduce the possible side effects of the radiation therapy the treatment will be given using special techniques to shield as much of your normal body tissues as possible. This method of treatment is called conformal intensity modulated radiation therapy, or IMRT.

Inclusion Criteria:

• Histologic diagnosis of adenocarcinoma of the prostate within six months of entry
• Clinical stage T1B, T1C, T2A-C NX MO (see Appendix 1 for staging). Any Gleason score is eligible for entry, but Gleason score must be determined.
• Patients with a PSA >10.0 and Gleason score of 7; or patients with any PSA value and Gleason score of >8 must have clinically negative lymph nodes as determined by a pelvic CT scan done within 12 weeks of entry. A negative bone scan is required before entry for all patients with Gleason score >8, or any patient with a Gleason score of 7, and a PSA >10.
• The patient must not have received any cytotoxic anticancer therapy. Previous or concurrent hormonal therapy for local disease is acceptable.
• ECOG performance status of 1 or less
• Age 80 years old or less
• Serum PSA <25 ng/ml within 4 weeks of study entry
• Informed consent

Exclusion Criteria:

• Patients with history of inflammatory bowel disease or other contraindication to radical radiation therapy
• Patients with prior colorectal surgery
• Any prior pelvic radiotherapy. Any prior TURP done <12 weeks from study entry.
• Any previous cytotoxic chemotherapy
• Patients with prior malignancy except non-melanoma skin carcinoma within 5 years of the diagnosis of prostate cancer