To evaluate different study designs and the general utility of phase II trials on prostate cancer.

Extensive literature studies and correspondance within the working group during 1 year were summarized in a preliminary manuscript. The manuscript was finalized at a 1 day meeting and is presented here as a consensus document.

The main objectives of phase II studies are to assess whether a treatment is sufficiently active to justify comparative phase III studies, and to obtain further information on adverse reactions. Bidimensionally measurable lesions are traditionally studied, allowing objective criteria for response and progression to be applied. However, as skeletal metastases do not fulfill the criteria for such lesions, the majority of patients with metastatic prostate cancer are not eligible for traditionally-designed phase II trials. Therefore, ancillary response parameters, especially serum prostate-specific antigen (PSA), have been proposed for use. For the evaluation of adverse reactions, the criteria of the World Health Organization were proposed for use. A review of various statistical designs was presented, with a focus on their advantages and disadvantages in phase II trials.

The role of PSA in phase II trials has not yet been firmly established. Further study of its correlation with other endpoints is needed. In future phase II trials, a shift to softer endpoints than traditionally used may enhance the process of evaluation of new antitumor drugs. Phase II studies may even be replaced by early phase III studies, especially in situations where new drugs do not have very heavy adverse effects.