 - Number of patient : about 70 evaluable patients .Simons optimal two-stage design will be used to allow early termination should sufficient evidence of non-effectiveness are collected. Thalidomide is considered non-effective if the proportion of PSA response is 14 or lower, and is worthy of further study if the proportion of response is 30 or higher. Controlling the risk for accepting thalidomide when it is non-effective to be at most 5 and the risk for rejecting thalidomide when it is effective to be at most 10, this design calls for 26 patients at the first stage. If four or less PSA response is observed, then the study will be terminated. Otherwise, additional 44 patients will be entered at the second stage. The treatment will be rejected if a total of 14 or less PSA responses are observed out of 70 patients. This design has 70 chance of termination after the first stage if the true PSA response rate is 14 or lower. With 70 patients, the study will provide 95 assurance to claim that the difference between the estimated and true proportion will be within 11. 