I do not recall my dad having any hallucinations from the treatments for either of his cancers. He did earlier experience a urinary tract infection that, believe it or not, has as one of its symptoms hallucinations which went away after treatment with antibiotics. This was in the form of hearing sounds that were not there.
At this stage, though, during end of life care, there are hallucinations and strange dreams from the progression of his disease. They treated this with Haldol or haloperidol, that has worked amazingly most of the time.