I'm sorry, too, to hear about the tumours.

The PSA is a warning sign that the tumours are there (in your case), and probably — but not definitely — will decline once you've dealt with the tumours. If it doesn't, or rises again later, that might be a warning sign that something else is going on.

PSA in itself is harmless, but it warns us we need to look for something. In a sense, it's the fire alarm, not the fire.