Behavior under megestrol/Ovaban

My cat has been taking megestrol acetate (Ovaban) for about
a month - palliative treatment for terminal cancer. The
oncologist said it would help appetite and "make him feel
good". Appetite is very good but behavior is weird and I'm
having a very difficult time judging whether it is the result
of the drug or progression of the cancer (and the inevitable
decision of when to do euthanasia). The oncologist has bailed
out - they may be trained to do this after a terminal Dx, I
have seen it before with another specialist. The regular vet
doesn't know about the drug ... gave me a copy of a description
from some vet reference book, which includes "personality changes"
under adverse effects but without any details.

Has anybody here had a cat on Ovaban? What sort of behavior
changes did you notice?

Thanks,
Roby