I too am amazed and horrified that doctors recommend Prolia seemingly without a thought of how do you get off of it. Not everyone gets multiple spinal fractures when stopping Prolia but the risk of those fractures is significant. And while it is perhaps not clearly defined how many people will get those multiple fractures it is clear that there is a significant risk for a very bad outcome. Your life could just get chaotic for whatever reason and you miss your shot and then a few months later you start fracturing!
People confuse this issue by thinking that Prolia is just like the anabolics in that you lose bone quickly after stopping it. But it's not the same. With the anabolics you do lose bone but you don't start getting multiple spinal fractures. In fact there's a study showing that your fracture risk stays improved for up to 1.5 years after stopping Forteo even though you are losing the bone density you gained while on it.