I was told by my endo that I would be on mess to lower my prolactin levels and they would monitor the size of it by doing MRIs annually. They said some times the meds will make the mass shrink and it could "die"
Now I've personally never gotten to a maintenance status. I ended up pregnant 6 weeks after starting dostinex in Feb of 2011. I started meds again May of 2012 to help stopping breast feeding then 3 months later I was pregnant again! Both times on birth control and after being told by two endos I would need fertility treatments to get pregnant!
I think you mean that your wife has a prolactinoma - a pituitary tumor? She took the medication - and the levels did go down.
She will have to continue to take the medication forever - or the tumor's effects will simply come back or the tumor will grow. She should be under the care of the doctor to monitor the tumor always - and it may be that the dosage can be moderated after a time, but she should always need something.