Table of Contents

Chapter 5: "Secondary" Local Treatment

i. PSA Velocity

Suppose one man underwent intensity-modulated radiation therapy (IMRT), and his PSA nadir was 0.15 ng/mL. Over the course of nine months, it slowly creeps up until it hits 0.45.But his brother, who also underwent IMRT, nadired at 0.32 ng/mL. If after the same progression over the course of nine months his PSA also rose to 0.45, are they now in the same place? Or is there some significance to the fact that one man’s PSA rose much more rapidly than his brother’s?

The rate at which your PSA rises after prostatectomy or radiation therapy can be a very significant factor in determining how aggressive your cancer is, and can therefore be useful in determining how aggressively it might need to be treated.

When looking at PSA velocity in a few hundred men who had undergone either prostatectomy or radiation therapy, researchers found that men whose PSA doubled in under three months had the most aggressive tumors and were more likely to die from their disease, whereas those whose PSA doubled in more than ten months had the least aggressive tumors and were less likely to die from their disease.

If we go back to our two hypothetical cases, although both have a PSA of 0.45 ng/mL, the first one, whose PSA rise represents a doubling within nine months after treatment, would likely be considered for an aggressive therapeutic regimen. And the second case with the smaller rise in PSA? He might be watched closely to see how rapidly his PSA rises, and to determine when it might be time to intervene.

However, PSA doubling time or velocity does not always remain the same over time. So even if you have a very slowly rising PSA now, continued monitoring with your doctor is important. Also, if you’ve consistently kept to a very low PSA rate after treatment, any rise will likely be seen as a signal that the tumor might be starting to grow again.

Measuring and using PSA velocity is an art, not a science. There’s no magic number of times that your PSA has to be tested in order to determine the rate of rise, although most researchers would agree that more frequent tests over longer periods of time will likely give a better sense of how your tumor is growing.

Ultimately, PSA is only one of many factors that can influence the decision to pursue additional treatments. You and your doctors will need to weigh all of the different factors before deciding on the course that’s right for you.