Hormone Therapy (HT) will normally stop PC growing for a while.
It's given in the case of having curative radio therapy (RT), usually for a few months before, and anything up to 3 years afterwards if the RT is believed to have killed all the cancer, because it makes the RT significantly more effective and the cancer less likely to return.
If the PC is not curable (e.g. mets in bones or other distant mets), then HT is given for life, but chemo is likely to be used too, sometimes early on, sometimes only when HT starts becoming less effective.