Could be prescribed off label perhaps but might not get insurance coverage
But it cannot be manufactured off label. And that means they cannot manufacture with tumors from other organs.
I could some see modest off-label use at the edges. Some grade 3 where they did not run the genetic scan for IDH. A patient who was a bit too sick. But I would be surprised if the system allowed random tumor material to be submitted without being detected.
I would also doubt any doc would submit tumor material into the process that is not in accordance with the label. That goes well past off-label use.
Not that any of this matters.
EDIT: I will be a stronger. If non brain tumor material is used it is no longer the approved drug. Any Doc who would do this is not just going off-label, but treating with unapproved drugs.