12 years ago, before Optune, I kept my wife alive for 3 years in part by taking the supplements recommended in Ben Williams book on his experience in surviving a very invasive GBM for over 10 years. We also made sure that her diet eliminated carbohydrates which contain large amounts of sugar. Sugar causes geometric increases in the growth of brain tumor cells. She also had some success taking Tarceva to limit tumor growth. Things were going quite well with 2 resections and rad and temodar but unfortunately another GBM appeared in same frontal lobe as the original tumor and her age (66) prevented the oncologists from trying to treat both tumors.
I have heard some really good info on the Optune success in extending the lifespan of GBM patients, and also have heard positive things about the results of a Phase III vaccine trial (Tacogen the research firm). I am keeping up with brain tumor research because my son has Phase II diffuse astrocytoma. Seems he has picked up my wife's DNA makeup.
Wish your husband the best.

Richard