Glioblastoma Grade Iv How Long Is A Treatment Plan With The Drug Avastin ?

How long is a treatment plan with the drug Avastin ? - glioblastoma grade iv

My son has a glioblastoma multiforme grade IV, and received chemotherapy and radiotherapy. He has just started on injections of Avastin every two weeks. Just wondering what the end of this treatment. His doctor said if he reacts to follow with Avastin