Dar,
DRE is a lousy test - so is PSA
As we get older, there are calcifications and benign cysts that crop up. PSA goes up naturally with age and prostate size and is not specific to prostate cancer. There is another (lousy) blood test - % free PSA - that can add another piece to the puzzle. Putting all of those lousy tests together, and eliminating sources of error like prostatitis and BPH, it might indicate that a biopsy is worth doing. Standard biopsies are less lousy than the previous tests (they are random and can miss stuff).
I agree with John T that a positive DRE is worth exploring. Perhaps get another finger up there to confirm. They can also do a cheap, quick and non-invasive pelvic ultrasound probe to see if that shows anything, and perhaps more importantly, to get a size reading on your prostate. PSA density - PSA divided by the prostate size - is an indicator of PC -- less lousy than PSA alone.
- Allen