It is about probabilities. When the PSA falls low post op and then rises by small amounts, that is a classic behaviour of small clusters of cancer cells left in the prostate bed so salvage RT would be offered, usually with HT.
If the PSA stays high after RP (over 0.2) and / or rises rapidly, that is the behaviour of mets or micromets so salvage RT is unlikely to work. In that case, HT is likely to be the main holding treatment with or without chemo - this would not be curative. If a scan can pinpoint one or two mets then some targeted treatment might be offered in some areas of the country.
It seems that if you do have a recurrence on your hands, Lynn falks safely into the first group.