glioblastoma multiforma

My husband was operated on for a glioblastoma multiforma 9/11/07.  He was on Keppra for seizure prevention, he had a seizure 2 weeks later and was given dilantin as well.  About a month after surgery he had daily Temodar and directed radiation (5x/wk) for 6.5 weeks.  A month or so after the treatments he was given an increased dose of Temodar for the first 5 days of each month.  During this time he seemed to be cycling between relative health and vigor and loss of balance, energy, cognition, etc.  The recovery seemed to be less complete and the losses greater each round.  The doctor seemed to think that my husband was not tolerating the chemo very well.  He decided to discontinue.  After he took a new job and we received a new doctor he decided the treatments should continue for 3 more rounds.  Within 6 hours of the first chemo pill (round 4) my husband could not walk, stand, talk, he was incontinent, he had a rash on his face and head, his legs were a livid purple from the knees down.  We discontinued further treatments since my husband never really gained health.  He spent 5 weeks in rehab, the first 4 weeks were very good (walking with a walker) and the 5th week he "crashed" (could not even stand.  From there he went to Adult care and within 3 days was not using the wheelchair.  At the end of a month he was able to go out to lunch one day and to church the next.  Then he "crashed".  He had an MRI at this time, while he was still able to transfer to a wheelchair.  The results of the MRI showed no active brain tumor, new or old.  He quickly became bed bound then on hospice.  He died about 2 weeks after his MRI.  All along all blood work, medication levels, hormone levels, organ functions, ect. were normal.  So my question is :  What killed him?