It depends. Survival rates for any cancer are very dependent on a number of variables. With astrocytomas, patient age, tumor location, pathological features (anaplastic versus low-grade, presence of necrosis, 1p/19q deletions, etc.), complications from treatment (radiation or surgery), and functional status all seem to affect prognosis.
Astrocytoma. The brain tumors are graded i-iv, wth the i -iii carring astrocytoma as part of their name. Survival and function is best at lower grades, some of which are not treated. Location is another issue, because you cannot safely resect in fluent or functional areas. Grade IV is gbm.