Found the following quotation from Mayo Clinic Proceedings, February 2007,
which supports Jerry1's post.
Ultimately, the decision to start androgen ablation therapy in the setting of biochemical failure is based on one of several trigger points used in the clinical setting, for example, a predetermined PSA level that will trigger the initiation of therapy, such as an arbitrary PSA level of approximately 10 ng/mL or a PSA doubling time of less than a year. The PSA doubling time enables an assessment of the likelihood of progression, which can be useful to discuss with patients in deciding when to initiate hormone therapy. There is an increased rate of metastatic disease when the interval between primary treatment and PSA failure is short (≤2 years) with a rapid PSA doubling time (<10 months).8 Unfortunately, no real data exist to aid in this decision-making process. Often, it is simpler to begin therapy, but caution regarding impact on quality of life and clinical benefit must be considered. Patients who opt for active surveillance will require ongoing discussions regarding the risks and benefits of deferred therapy. Clinical trials would be optimal to help address this dilemma.
Doesn't make the decision any easier, does it?
Best of luck!