The commonest type of primary brain tumour in adults is called a high-grade glioma.  Unfortunately these are usually quite aggressive tumours and often too big for surgery to be possible by the time they are discovered. 

Sometimes, however, an operation can be done to try and remove the tumour.  Recent studies have suggested that sometimes the results of surgery can be improved by putting wafers containing a chemotherapy drug into the space in the brain where the tumour has been removed.  These wafers contain a drug called carmustine, or BCNU.  The wafers (also known as Gliadel wafers) slowly release the drug into the nearby brain tissue over about 5 days, and the wafers themselves dissolve completely over a few weeks.  With this very localised type of chemotherapy there do not appear to be any upsetting side-effects.

Because it appears to be a safe treatment, that may improve the outcome for some people, neurosurgeons will often use this as an adjunct to their surgery in selected patients with high grade brain tumours.