My condolences also to you Branno. Spread to the brain from another site such as lung is FAR commoner than a primary brain tumour. This is almost certainly the situation with your late father. Probably 1/5 lung cancers already have involvement of the brain when they're diagnosed ; these secondary brain tumours tend to be multiple and inaccessible to surgical removal.
Seve Ballesteros was still a fairly young man, with three children - his cancer was of a type which was unlikely ever to be cured. Other types of primary brain tumours ARE curable.