Sen. John McCain addressed his cancer prognosis Sunday on CNN's "State of the Union," presenting a optimistic view in his first national interview since receiving his diagnosis.

"I'm fine," McCain told anchor Jake Tapper. "The prognosis is pretty good. Look, this is a very vicious form of cancer that I'm facing, but all the results so far are excellent."

McCain was diagnosed with brain cancer in July.

The Arizona Republican acknowledged the severity of the illness, but said it was the latest test in a lifetime of tough fights.

"I'm facing a challenge, but I've faced other challenges," McCain said. "And I'm very confident about getting through this one as well."

McCain returned to Washington as the Senate came back from its August recess last week, and he said he planned to focus in the coming week on a key defense bill, with a magnetic resonance imaging test planned for Monday.