Patients have for years noticed that they have become more forgetful or lose concentration soon after starting chemotherapy - but doctors have always denied any link, as they didn't believe the drugs could cross the blood-brain barrier.
But new research reveals they can, and do, and that 'chemobrain', as it's been dubbed by disbelieving doctors, is very real.
And despite denying it to their patients, doctors have been quietly documenting the cases for years, and now researchers fear chemotherapy may be more toxic to brain cells than to cancer cells.
Mark Noble and his team at the University of Rochester in New York have discovered chemotherapy can cause delayed brain degeneration, and even short-term use of the chemotherapy drug fluorouracil causes acute injury to the central nervous system.
(Source: Journal of the American Medical Association, 2008; 299: 2494).