I took was diagnosed with a 3+4 lesion in May this year. On the surface 3+4 (w/high percentage 3) looks like "favorable intermediate risk cacer", but your PSA velocity from 3.2 to 8 in 6 months is concerning if it was not caused by other factors like inflammation or infection. It turns out the 3+4 group is an extremely hetrogenous categroy with some in this group behaving biologically like 3+3 while others behave aggressively like Gleason 9 or 10. So, how do you know which subgroup you belong to? Fortunately, there are simple tests to do just that,

Given your high PSA velocity, you should ask your urologist to send a sample of the biopsy for a GPS (Genomic Prostate Score) test which will detemine the aggressiveness of the biology of your cancer. That is exactly what I did and my GPS score came out as 47 on a 0 to 100 scale: less than 20 being low risk, 20 to 40 being intermediate risk, and 40 to 100 being high risk. If my GPS score was less than 20, I was going to consider going on active surveillance, but given a score of 47, I agreed on a definitive treatment of prostatectomy which resulted in a final pathology of 3+4 but with several riks factors like seminal vesicle and extra capsular invasions.

So, in your case, I suggest you get a GPS test before deciding to remain or active surveillance or seek definitive treatment. I also concur with a suggestion earlier of geting Dr Patrick Walsh's book "Guide to Surviving Prostate Cancer" which is very comprehensive, readable, and understandable, with a summary at the beginning of each chapter to get a quick overview.