We're talking about glioblastoma here, there's not much "continous" treatment to be had and temozolomide's and bevacizumab's patents have run out (edit: also bevacizumab doesn't prolong overall survival at all and temozolomide is ineffective in MGMT-positive patients, i.e. about half).

That said, I'm not sure why the other commenter is so dismissive of your idea. There's plenty of drugs that have been kept in the cupboard (e.g. desloratadine) or not seeking approval for certain illnesses so a "new", more expensive drug could be sold (e.g. no rituximab trials for multiple sclerosis so Roche could sell Ocrelizumab, no Bevacizumab trials for macular degeneration so they could sell Ranibizumab) – and certainly many more that we never heard about.