For the individual patient, radiation provides usually an equivalent form of treatment. However, if in the long term, there is a distinct advantage for radical prostatectomy over other treatments, albeit possibly slight. Watchful waiting has a role in prostate cancer treatments although this role, in my opinion, is clearly limited to a select few patients. The scenario could also include a man in his later years who, by means of an elevated serum PSA, is found to have prostate cancer on prostatic biopsies. This man can also be followed by watchful waiting.
Age is an important factor.
However, the patient's individual preference is also important. If the serum PSA is tremendously elevated, then this might not be a good option, as other forms of treatment like hormonal treatment exist. People are interested in watchful waiting because of the obvious concerns for side effects for prostate cancer. These include sexual potency, urinary incontinence, and a decreased libido that can specifically happen with hormone deprivation therapy. Some men are interested more in the quality of life than the quantity of life.