Chemobrain refers to a syndrome (a bunch of symptoms) that some people get when they take chemotherapy drugs. Chemotherapy is a systematic treatment, meaning it goes all over the body. An unfortunate side effect of many chemotherapy agents is a diminshment in mental energy and acuity. As a stimulant, modafinil has found some interest from doctors for treatment of this condition.
The American Psychiatric Association published an article about modafinil for teatment of chemo-brain in breast cancer patients.
http://pn.psychiatryonline.org/cgi/content/full/42/15/31
A recent University of Rochester study showed that Provigl is effective in treatment of chemobrain