Brain tumours may either be primary or secondary.  A primary brain tumour is one that starts in the brain, a secondary brain tumour is a seedling, or seedlings, of tumour that have spread to the brain from a cancer somewhere else in the body.

In adults the commonest type of primary brain tumour is called an astrocytoma.

By looking at samples of tumour tissue (biopsies) under the microscope, doctors are able to group astrocytomas into four grades, I to IV.   Grade I and II astrocytomas usually behave very differently from grade III and IV tumours: grade I and II astrocytomas tend to grow very slowly, often remaining static for years at a time, whereas grade III and IV tumours are usually very aggressive, growing very rapidly indeed. 

Grade I and II tumours are often called ‘low-grade’ astrocytomas, and the grade III and IV tumours are called ‘high-grade’ astrocytomas.  (Rather confusingly, astrocytomas are the commonest type of a group of primary brain tumours called gliomas, so these tumours may also be called low-grade, or high-grade, gliomas.)

If scan tests and biopsies have shown that someone has a low-grade astrocytoma then the next question is ‘what treatment should be given?’.

If tests show that the tumour is quite small, and is in a part of the brain where it is safe to operate, then surgery may be recommended.  The aim of this is to remove the tumour completely.  This treatment does offer the chance of a cure, but it is only possible for a few carefully selected people with low-grade astrocytomas.

Most people with low-grade astrocytomas are not going to have tumours that can be completely taken away by an operation.   Studies in the past have shown that in this situation doing an operation to remove part of the tumour (sometimes called ‘debulking’) really doesn’t help and does not improve life-expectancy.  So ‘partial’ surgery is not really an option.

Radiotherapy can help to control low-grade gliomas for a period of time, slowing or arresting their growth for a period of months, or even years.  However, because they are often very slow growing, many low-grade gliomas cause very few problems or symptoms for some years after they are first discovered.  Clinical trials have shown that delaying giving radiotherapy until the tumour is clearly getting bigger, and causing troublesome symptoms, is just as effective as giving radiotherapy at the time when the tumour is first diagnosed.

This means that for most people with a low-grade astrocytoma, that is not suitable for a complete surgical removal, there is a choice between having radiotherapy immediately or keeping the treatment in reserve until symptoms (like fits, seizures, or headaches) become a nuisance.  As this can often mean putting off treatment for some years many people decide that this is what they would like to do.  

Those people who do decide to delay their radiotherapy will then usually have regular check-ups, every few months, and have scans repeated at intervals to check that their tumour is still relatively inactive and not showing any obvious signs of growth.

It sounds as if your friend has opted for this ‘wait and see’ approach, which is a perfectly acceptable way of managing her situation.

Reference

Tumours of the central nervous system. Oxford textbook of oncology.