@asolidrock As far as I understand, there's not a one-to-one mapping between PSA and the severity of the prostate cancer, but in general, a higher PSA does indicate a more aggressive or widespread cancer. My PSA was about 68, and I almost permanently lost mobility and sensation blow my ribs because it compressed my spinal cord so rapidly.

I think the old rule of thumb during initial screening (before a person had any treatment) was that a PSA of 10 represented about a 50/50 chance of actual prostate cancer. A PSA of over 20 almost certainly meant cancer. But PSA alone was a very blunt diagnostic instrument.