Sen. John McCain, American ‘maverick’ and political giant, dies at age 81 after battling brain cancer. The six-term U.S. Senator from Arizona disclosed in 2017 that he had been diagnosed with a deadly form of brain cancer called glioblastoma. Before his three-decade senate career and a run as the Republican presidential nominee in 2008, McCain endured more than five years as a prisoner of war in Vietnam. Ref. USAToday.