I was wondering what are the chances of recovery for a patient affected by astrocytoma grade iii?

Depends on location: If your question is whether the patient may recover from the symptoms of the the tumor, it depends on the size, the location, the extent of surgery and the response to chemotherapy/radiation therapy. If your question is whether the person will ever be cured of the tumor, that is unlikely. You can hope for long term remission(5-10 years)and the possibility of new therapies that are on the horizon.