PCa Commentary
 

Post Therapy PSA Doubling Time Of <3 Months Is A Surrogate For  Prostate Cancer Specific Mortality (Nov 2003)

It is intuitively known that a rapid post primary treatment rise in PSA is an adverse predictor for survival. However, quantification and refinement of this relationship was the subject of a study by D'Amico et. al. in the September 17, 2003 issue of the JNCI: "Surrogate End Point for Prostate Cancer-Specific Mortality After Radical Prostatectomy or Radiation Therapy." The analysis was performed on the combined CAPSURE and CPDR data bases involving 8669 men with localizedor locally advanced, non-metastatic disease. 5918 were treated with RP and 2751 with radiation. PSA was evaluated q 3 months for 2 years, q 6 months for 3 more years, and then annually. The median follow-up for the 1451 treatment failures was 4 years. The minimum PSA level for calculating the PSA-DT (doubling time) was >.2 ng/mL (the biochemical failure point) and doubling time was based on at least 3 PSA measurements with a requirement that each increase was > .2 ng/mL. In order to establish a common PSA starting point for DT estimation between the two types of treatments, in calculating the PSA-DT for radiation patients the post treatment nadir PSA value ("typically less than 1.0 ng/mL within 2 years after radiation therapy") was subtracted from any subsequent measured PSA. For example if the nadir had been 6 ng/mL and a subsequent measured PSA was .9 ng/mL, .3 (a "failure" since it exceeds .2) would be entered in the DT calculation for that data point. Their conclusion: the cohort with a < 3 month PSA-DT after PSA failure had a nearly 20-fold increased risk of prostate cancer-specific mortality compared to the > 3 month cohort, and "the median survival after PSA-defined recurrence in such patients is only 6 years." By validating our intuitive concern in this matter, the authors provide a strong rationale for the early institution of additional therapy in this high risk group.

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