To OP: that has been a big issue for years for those of us in the field. Especially, if your territory has no real treatment centers (lack of facility resources/specialists for pheresis, small practice hesitation at working with such an expensive drug with a company that has a strict no return policy regardless of situation even if the patient does not show/transfers to different practice/expires, or transfers to a "big"/academic institution because their physician has no experience in the disease and they want a specialist who has (think "life threatening condition with their loved one/child")
The rep w the territory where the "drug goes in the vein" gets the start credit for quota and payout. When the patient returns home for treatment (every 2 weeks, forever), the original referring territory is responsible for maintaining the patient on treatment.
Problem is the "less expert" MD still has concerns, often isn't convinced the patient needs the $$$$$ therapy, and lets the patient stop (other reasons, too) Then the original rep gets "hit" for the lack of retention. And never even got paid on the patient start.
It makes a huge difference to that rep especially because there are so few patients in existence, and there isn't consistent clinical agreement that either indication needs to be treated chronically