fPSA is a variety of PSA.  Don't get hung up on bound and unbound.  This
type of PSA exists most often with non-cancerous prostate cells.  So, the
greater the percentage of fPSA, the less chance you have of having cancer.
Anything over 25% is usually really good.  Anything under 10% is usually
indicative of requiring aggressive treatment.  Anything between 10% and 25%
is a gray area.  If you are not diagnosed already, an fPSA in this area is
not very useful to predicting prostate cancer.  However, in your
circumstance, in that you are already diagnosed, if your fPSA is between 10%
and 25% that indicates less of a need for aggressive treatment.

Do you know your fPSA?

"Bound" means chemically bonded.  The PSA molecule is chemically
bonded to a protein molecule in the blood.

The Wikipedia article on "Prostate Specific Antigen" has a graph
showing the relationship of free PSA and prostate cancer.  The
research on which the graph is based claims a 55% chance of
cancer in men with fPSA <= 10% and a less than 10% chance
for men with fPSA > 25%.

Click on the graph to see it larger.

   Alan

The last time I checked, which was a while back, if the free PSA was
below a certain level, that made prostate cancer more likely.  How high
the odds were depended on the details of the case, but I think in most
cases the odds were still in favor of the patient not having prostate
cancer despite a low fPSA.  fPSA was used primarily to determine if the
risk of prostate cancer was high enough to merit a biopsy.  Walsh in his
book didn't recommend the routine use of fPSA, but he said it was useful
in borderline cases, where a first biospy was negative, to decide if
repeat biopsies were warranted.

I haven't followed the research literature on this issue since then, but
at one time it wasn't clear whether or not fPSA told you anything about
how aggressive the cancer was and the likelihood of cure. ron will
probably know more about that and maybe he will chime in.

In a nutshell, PSA is converted to fPSA by proteins in prostatic
cells.  When cancer is present, the cell ducts become disrupted and
leakage from the cells occurs more readily.  Hence, there is less time
for proteins to convert PSA to fPSA
and the amount of fPSA produced is diminished, leading to an decreased
ratio of fPSA/PSA.

But more importantly, I don't think this matters in your case.  Your
PSA is 2.13, the effectiveness of the fPSA/PSA ratio as an indicator
of the presence of PCa has not been demonstrated for values of PSA
below 2.5...ron