WASHINGTON: Veteran US Senator John McCain, a onetime prisoner of war and the 2008 Republican presidential nominee, has been diagnosed with brain cancer, his office announced Wednesday.

The 80-year-old lawmaker underwent surgery to remove a blood clot from above his left eye last week and tests "revealed that a primary brain tumour known as a glioblastoma was associated with the blood clot," the Mayo Clinic said in a statement released by McCain´s office.

"The senator and his family are reviewing further treatment options," the statement added, noting they may include a combination of chemotherapy and radiation.