This is a serious diagnosis and his prognosis, from what I understand on these types of tumors, is not good. Same type Senator Kennedy had.
http://www.cnbc.com/2017/07/19/senator-john-mccain-has-a-brain-tumor-his-office-says.html
http://www.cnbc.com/2017/07/19/senator-john-mccain-has-a-brain-tumor-his-office-says.html