Inclusion Criteria:

1. Adenocarcinoma of the prostate with the following high-risk features are eligible: clinical T2c, clinical or pathological T3 or T4 disease OR Gleason 8-10 disease OR PSA > 20ng/ml.
2. Patients must have no evidence of metastatic disease by clinical and radiological staging including Chest X-ray, Bone scan and CT Scan of the Abdomen and Pelvis.
3. ECOG Performance Status 0-1
4. Calculated Creatinine clearance > 35cc/min, Absolute neutrophil count > 1,500/mm^3, Platelets >/= 100,000/mm^3, AST/ALT < 2.5 x UNL, Total bilirubin WNL.
5. No standard contraindications to radiation therapy including prior radiation therapy, inflammatory bowel disease, irritable bowel syndrome, or and collagen vascular disease.
6. Patients must be at least 18 years of age
7. Patients may have had up to 8 weeks of hormonal therapy defined as luteinizing-hormone releasing hormone or other medical castration therapy prior to registration.

Exclusion Criteria:

1. Prior VEGFR/PDGFR inhibitor or other investigational therapy.
2. Inability to take oral medication
3. Chronically uncontrolled hypertension, defined conventionally as consistent/repeated systolic pressures above 140 mmHg or diastolic pressures above 90 mmHg despite anti-hypertensive therapy. This may be established with home BP readings. There is no criterion related to a specific BP result required for eligibility, nor are acute BP elevations that are related to iatrogenic causes, acute pain, or other transient reversible causes considered an exclusion criteria. The intent is to exclude patients with chronically uncontrolled hypertension that might be further exacerbated by Sunitinib.
4. Left Ventricular Ejection Fraction </= 40%, symptomatic congestive heart failure or symptomatic ischemic heart disease, deep venous thrombosis or pulmonary embolism in the last 12 months.
5. Known human immunodeficiency virus infection, alcoholism, chronic active hepatitis or liver cirrhosis