• Gleason Grade at diagnosis
• Occurrence and quantity of HGPIN at biopsy
• Percentage of core involved at diagnosis
• Number of cancer positive cores

This 4-year study will compare how safe and effective an oral investigational medicine is (compared to placebo) in preventing the development of prostate cancer in men that are defined by the study entrance criteria as being at an increased risk for prostate cancer. Study visits to the clinic will occur every 6 months for up to 4 years (10 clinic visits), and a prostate biopsy will be performed at 2 and 4 years of treatment.

• Drug: Dutasteride
• Drug: Placebo

• Placebo Comparator: Eligible subjects will complete a 4-week placebo run-in followed by randomization to either 0.5mg dutasteride or matched placebo in a 1:1 ratio.
• Experimental: Eligible subjects will complete a 4-week placebo run-in followed by randomization to either 0.5mg dutasteride or matched placebo in a 1:1 ratio. Randomization will be stratified by center.

Inclusion criteria:

• Informed consent to participate in study.
• Have had a single negative prostate biopsy within 6 months prior to enrollment in study.
• Have a PSA (prostate specific antigen) between 2.5 and 10 if 50-60 years of age; or a PSA between 3.0 and 10 if over age 60.
• Ability and will to participate in study for 4 years.

Exclusion criteria:

• More than one previous negative prostate biopsy.
• History of prostate cancer.
• Previous prostate surgery.
• Inability to urinate requiring the need of a catheter during the previous 2 years.
• Any condition (other than benign prostatic hypertrophy) which may result in urinary symptoms or changes in urine flow rate.
• Cancer within previous 5 years (other than basal or squamous cell cancers of the skin).
• Any unstable serious medical condition.
• Use within the past 12 months of finasteride (Proscar or Propecia), dutasteride (Avodart), testosterone, or drugs that can block the action of male hormones.