GBM after two years of treatment survival of 69 year old man?

My husband 69 years was diagnosed with a glioblastoma grade 4. He had surgery, radiation and chemo. It has been two years and the GBM shows to be growing back. How much time does he have to live. Right now he is doing pretty good. He still drives. He says he doesn't hurt. He does has memory loss and gets very tired, he also is very hyper and compulsive. I am getting worried.