It's my understanding that PV IS a blood cancer, it's a progressive disease with no cure..There are medications to help with the symptoms and slow the disease and clients who have it can live many years under the care of a hematologist...I also understand and experienced that general practitioners are not aware these cancers exist and don't pick up on the diease..even after a TIA or clotting incident. I wish things were different but the reality is as I said. So your question on prevention, there isn't one since they don't know the cause that causes the Jak2 mutation switch to get stuck on the on position. For now, if your lucky enough to get it diagnosed is get under the care of a specialist and treat the symptoms., slow the disease and crave out the best life as I promise you even though we're living with the symptoms everyday it could be much, much worse....Accepting the realities is a first step....