Surgical intervention for spinal tumors is intended to prevent further deterioration in patient's mobility or quality of life.  Ideally, the tumor is completely removed, but the location or type of tumor may make that impractical. 

The following figure is an example of the decision process that a clinician might go through before scheduling the patient for surgery. Neurosurgeons consider many factors before deciding to do surgery, and every patient is different.  Your neurosurgeon will discuss with you the factors relevant to your case.

What this diagram means is that first the neurosurgeon considers the effects of the tumor on the patient's daily life (pain, ability to stand and walk, etc).  Next, non-invasive methods, and their possible benefits, are weighed against the growth of the tumor and the condition of the patient.  Surgery is performed when it is clearly the best option for the patient.