Hi Martin,
I was offered AS after a template biopsy, Surgery or Radiotherapy 8yrs ago. At the time my diagnosis was 4+3, T2/T3a(?), lesion size 13mm. After the op it was found to be 4+4 T2a. What tilted my decision for action was that it was said to be near the edge of the prostate.
I'll never know if surgery was the best option but it did give me a fast solution and a definite answer i.e. psa<0.05 or undetectable. Although 5yrs later it became 0.06 detectable and after 8yrs it's 0.12, an amazingly slow rise and an offer of RT without a scan or wait another three years at current trends and hope a scan will see it.
After I chose treatment 8yrs ago the consultant said they offer AS so they aren't thought to be over treating. In your case it might be alright for a short while, with your psa and rise being a judge. Although as said above the location of the lesion might be a factor. All the best, Peter