I find it odd that this doctor didn't suggest a different benzodiazepine. If he knew what he was doing, he'd know that you can't just suddenly stop taking them and not expect a massive increase in anxiety symptoms. You have to taper down.
Wait, was "this person" even a doctor? I've googled to see if I can find the research article, and all I can find is that clonozepam is currently one of the recommended treatments for the anxiety that comes with being diagnosed with glioblastoma (or any cancer)!
I'm a working scientist - I have a PhD in biochemistry - and I'd never take second-hand information about a research article from someone, people always get it wrong. I have to read it for myself.