help me please

my mother had a meningioma removed in 1986. it returned in september 2005, this time it was tennis bgall size with leads. they removed it and she underwent several treatments of chemo and radiation,the tumor was tested and found to be benign. it returned in december 2006 at which point she under went several lazer knife treatments and chemo by september 2007 it was resolved. it is now back again. the doctor says he is baffled over the tumors insitance exspecialy since it has tested benign. neuro oncologist and surgion says shes had too much radiation and her body cant take anymore so lazer knife is out of the question. if he surgicaly removes it then it will just return and he cant keep doing that to her every 6months. there is new procedure in experimental phase but insurance might not cover it and she might not be able to tolerate it. with out surgery [at the rate the tumor is growing] she might survive 6 months. the procedure suggested is removing tumor and implanting balloon of chemo at the site. how effective is this procedure? why is this tumor so persistant? is this a hereditary issue? is it common for meningiomas to be this persistant?