Apples and oranges: building a consensus for standardized eligibility criteria and end points in prostate cancer clinical trials.

Abstract

To survey eligibility and response criteria for clinical trials in hormone-refractory prostate cancer (HRPC). Thirty-five established investigators of HRPC completed a 125-question survey. There was a general consensus that criteria for clinical trial entry would include progression based on an increasing prostate-specific antigen (PSA) level (94% of investigators), an increase in measurable disease (91%), and/or appearance of new bone lesions on bone scan (83%). Most believed that castrate levels of testosterone (77%) and progression after antiandrogen withdrawal (97%) should be documented before study enrollment. Continuation of testicular androgen suppression would be required by 82%. Seventy-seven percent favored separate reports on response rates in bone, measurable disease, symptoms, and biochemical markers (primarily PSA levels), rather than a composite response. Ninety-four percent of the investigators accepted changes in PSA level as a surrogate end point of response. However, interpretation by these investigators of a PSA data set similar to what might be observed in a clinical trial showed marked discordance. Survival is the end point of most importance to 94% of these investigators. Response based on changes in measurable disease, time to progression, response duration, PSA level decrease, or quality-of-life improvement were of similar weighted value as a clinical trial end point and were rated as less important to these investigators than survival (P < 10(-8)). This survey indicates some consensus on eligibility and concomitant treatments for clinical studies in HRPC. The use of multiparameter assessment of response and PSA level as a surrogate end point have been widely adopted.