Going straight to surgery is pretty common, depending on the size and location of the tumour. Typically, when a tumour is completely removed, the pressure on the brain eases considerably and a full recovery is expected, but again depending on where the tumour is and how it is entwined around the brain structures. The fact a steroid reduced the size is positive. Typically these surgeries are successful on "routine" tumours, those that grow on the surface of the brain matter. Again, while it's hard to say without more details, there's usually little long-term effect following surface tumour removal.
Over the past few decades the process has become standardized, and success rates are very positive. Doctors tend not to discuss too much with patients for two reasons: they don't want to scare the patient, and if they are too positive and something goes wrong, there's a lawsuit and possible loss of professional standing coming. My suggestion is to get on the Web and research what you can, then explain to your brother. He has a right to know and understand what is going on.
Keep in mind tumours are not "cancer". There's no such thing as brain cancer. A tumour is just an abnormal growth, and can usually be removed in routine surgery. FWIW I went through this myself back in the late 1990s, and I'm purfuctlhry nurnal. :-Cool/"
Good luck to your brother, and stay positive.