Hi Vapersupreme. Welcome to the forum

I am not a doctor; however I had surgery for prostate cancer in 2010 and my PSA has been < 0.1 (undetectable) since that time.

There are a number of factors which can affect the choice of treatment.  The most important is the stage, which is divided into 4 groups: T1, T2, T3 and T4.  T1 and T2 cancers are still contained inside the prostate. T3 have begun to spread outside but are limited to the local region. T4 have spread widely.  In the broadest terms, T1, T2, and some T3 are usually curable; the remaining T3 and T4 are too late to be cured, but can often be successfully managed and controlled for many years. 

The next important factor is the "Gleason" score, which is a surrogate measure for the aggressiveness of the cancer. The score is two numbers (3, 4, or 5) which once used to be added together, but now are more commonly listed separately, such as 3+3, 3+4, 4+3, 4+4, 4+5, etc.  The lower the numbers, the less aggressive the cancer; the first number carries more weight than the second, so 3+4 is slightly less aggressive than 4+3.

There is also the PSA which you already know about. Once treatment has started, PSA is a very quick and cheap test which is very useful for monitoring how well treatment is working. 

I hope this information is helpful.  Perhaps when you know more you'd care to share with us.