Inclusion Criteria:

1. Male patients aged >18
2. ECOG performance status < 3
3. Patients with metastatic prostate cancer currently receiving 1st line hormonal therapy (LHRH agonists or surgical castration) and failing with raising serum PSA
4. Biochemical progression documented by three consecutively rising serum PSA measurements, each separated from the other by at least 2 weeks, with the last measurement being 50% or greater than the nadir PSA achieved after the last therapeutic maneuver (i.e. first line hormonal therapy noted above)
5. Demonstrated tolerance to a test dose of s.c. octreotide acetate injection at Visit 1
6. Elevated (> 40 U/L according to DAKO Elisa kit) chromogranin A plasma levels documented by at least two consecutive measurements
7. Liver function tests < 2.5 ULN, serum creatinine within normality
8. Serum PSA (50% increased value) above 4 ng/mL for patients with intact prostate and > 0.8 ng/mL for post prostatectomy patients at study entry
9. Immediate history of rising PSA < 10 months
10. Castrate levels of testosterone (< 30 ng/dL)
11. Life expectancy of > 6 months
12. Signed informed consent prior to initiation of any procedure

Exclusion Criteria:

1. Prior chemotherapy or other systemic anticancer therapy except for LHRH agonists, and/or non-steroidal anti-androgens (eg, flutamide, bicalutamide or nilandron)
2. Palliative radiotherapy less than 6 weeks (42 days) prior to planned entry date
3. Other investigational drugs within the past 28 days
4. Long-term (> 3 months) treatment with proton pump inhibitors
5. Uncontrolled blood hypertension
6. Other malignancies within 5 years prior to study entry, except for curatively treated non-melanotic skin cancer
7. Patients with another non-malignant disease which would confound the evaluation of the primary endpoints or prevent the patient from complying with the protocol