size of tumor treatment

my doctor found that i have a pitutary adenoma which affect on my vision and prolactin hormone secretion,my tumor size is 4*4*3.5 part of the tumor is in the brain,i make endoscopic surgery from my nose and it result a debulking in the tumor but the tumor size is still the same also my doc. told me that he cannot touch the part of the tumor that in the brain and he begin a medical treatment with dostinex for 3 months, i take 1 pill everyday so that to decrease the prolactine secretion and the tumor size also,my doctor told me that it is possible that we can make a gamma knife after these 3 months or brain surgery.

My question is, does the dostinex will make the effect that it will decrease the tumor so that it is possible to make gamma knife or by this size there is no hope and brain surgery is needed?(i have the MRI and CT after the surgery)