PSA Velocity and How It Is Used
PSA velocity is used to evaluate the trend in PSA over time. The idea is that the faster PSA rises, the more likely it is due to cancer. Cancerous tissue, along with the breakdown of cell membranes that can result from cancer, releases PSA at a faster rate. This is another way to evaluate a man with borderline PSA values who does not want to undergo biopsy at this time. An increase of 0.75 ng/mL per year or more (or 20%) is thought to suggest cancer. A more gradual increase is more likely related to the growth of benign tissue (BPH).
The downside of velocity measurements is that it takes at least 3 tests 6 months apart, therefore a minimum of 1 year, to get a value. And there is considerable variability in PSA, from individual variation (as much as 20% day to day), to lab test variability, to differences in velocity between men. Thus, while comparing trends in PSA values over time is useful, PSA velocity has not been accepted as a basis for making biopsy decisions. Its best use may be in monitoring the effectiveness of treatment for men with prostate cancer.
