Can necrosis cause tumor markers to rise?

Hi there. A quick question. My mother had gamma knife on 6 brain lesions a year ago. All have shrunk a bit since, except for one which started getting larger since Jan. Mother had another MRI today which showed it again got a bit larger. Neurosurgeon thinks it's most likely necrosis but wants to keep a vigilant eye on it. I know this has happened to many of you. What concerns me is that my mother's CEA rose dramatically (like Steph's) with the brain mets. From 1's to the 9's. Since June it's been between .6 and .9 . Now it's gone from .8 to 1.0. Should this trouble me? Is that change significant? or can necrosis cause CEA to rise a bit? Anyone's experience is truly appreciated.