We’ve known for some time that radiation therapy to the brain can cause problems with thinking and memory. Now, we are learning that chemotherapy is linked to some of the same kinds of problems. Research has shown that some chemotherapy agents can cause certain kinds of changes in the brain. Though the brain usually recovers over time, the sometimes vague yet distressing mental changes cancer patients notice are real, not imagined.
http://www.cancer.org/Cancer/News/ExpertVoices/post/2012/04/09/Chemo-Brain-It-is-Real.aspx
Chemo Brain: It is Real