Clinical Trials in Relapsed Prostate Cancer: Defining the Target

A re-examination of the methods of developing new treatments for patients with prostate cancer whose disease has progressed during hormone therapy is necessitated by the following: 1) the impact of prostate-specific antigen (PSA) testing on patient selection, 2) the increasing number of studies using noncytotoxic approaches, and 3) the lack of validated methods to report outcomes. PSA monitoring after primary therapy has increased the number of patients referred for therapy with a rising value in this marker or an asymptomatic change in a radionuclide bone scan as the only manifestation(s) of relapse. The development of drugs for this population of patients presents a unique challenge because the classical criterion used to assess efficacy in the phase II setting, i.e., the presence of objective changes in measurable disease sites, frequently does not apply. Since no approach has been proven to prolong survival, the highest priority must be placed on developing new therapies. Standardizing the methods for evaluating treatments is also essential so that promising strategies are pursued and inactive therapies are not developed further.