Sen. John McCain, R-Arizona, says battling brain cancer is a challenge but that his prognosis is "pretty good."

Speaking in his first interview since his diagnosis, McCain acknowledged the situation has been tough on his family but says he is optimistic. He says he has "faced other challenges" and he's "very confident about getting through this as well."

The 81-year-old Arizona senator says he will have a MRI Monday and that his test results so far have been "excellent."

McCain, diagnosed with Glioblastoma, an aggressive form of brain cancer late last month, has already successfully undergone his first round of radiation and chemotherapy and spent most of his recess at home with family. He returned back to Washington for work in the Senate late last week.