Defining prostate specific antigen progression after radical prostatectomy: what is the most appropriate cut point?

PURPOSE The most appropriate definition of biochemical progression after radical prostatectomy and radiation therapy is uncertain. We analyzed the effect of using various prostate specific antigen (PSA) end point definitions for defining biochemical progression after radical prostatectomy and attempted to determine the best PSA cut point to use. Aspects of the American Society for Therapeutic Radiology and Oncology (ASTRO) definition of biochemical failure after radiation therapy are also analyzed in our radical prostatectomy cases. MATERIALS AND METHODS A total of 2,782 men with clinically localized prostate cancer (cT1-T2) who had undergone radical prostatectomy between 1987 and 1993 were reviewed. All patients had regular PSA determinations from surgery through followup. Analysis was limited to patients who did not receive adjuvant treatment within 90 days of radical prostatectomy. Biochemical, PSA progression-free percent after radical prostatectomy was determined by the Kaplan-Meier method using several PSA cut points, including 0.2, 0.3, 0.4 and 0.5 ng./ml. or greater, as well as 0.4 ng./ml. or greater and increasing. Progression-free percent was also assessed using the ASTRO definition, which is 3 increases in PSA. To determine which PSA level was most appropriate to define progression after radical prostatectomy, the percentage of patients with a continued PSA increase after reaching each cut point was determined. The relationship between the maximum PSA within 3 years of surgery and subsequent development of clinical disease was also assessed. RESULTS Progression-free percent was dependent on the PSA cut point used. Biochemical progression-free percentages for cut points 0.2, 0.3, 0.4 and 0.5 ng./ml. or greater were 62%, 72%, 76% and 78% at 5 years, and 43%, 54%, 59% and 61% at 10 years, respectively. A subsequent increase in PSA was noted in 49%, 62% and 72% of patients who had PSA 0.2, 0.3 and 0.4 ng./ml., respectively. Subsequent clinical progression (local or systemic) was directly related to the maximum PSA attained within 3 years of radical prostatectomy (p=0.0001). Progression-free percent for definitions requiring multiple increases in PSA were dependent on when the event was said to occur. Backdating of events at or before the first PSA (ASTRO definition) resulted in poorer, short-term progression-free percent (78% at 5 years), with little apparent likelihood of long-term failure (78% at 10 years). Coding the event at the last PSA increase when all event criteria had been met resulted in more realistic progression-free percent estimates (85% at 5 and 59% at 10 years). CONCLUSIONS Biochemical, PSA progression rates vary markedly depending on the method used to define PSA failure. Methods that require multiple increasing PSA values, for example the ASTRO definition, give misleading results, especially if the event time is backdated. Standards for defining PSA progression would allow more consistent and comparable progression estimates after radical prostatectomy. PSA 0.4 ng./ml. or greater may be the most appropriate cut point to use since a significant number of patients with lower PSA do not have a continued increase in it.