His wife Cindy McCain took to Twitter to say that her husband was "doing well after his surgery".
McCain, 81, made public last summer his brain cancer diagnosis, and he's been recovering from side effects of the cancer treatment at his home in Arizona since late a year ago.
"Senator McCain and his family are grateful to the senator's excellent care team, and appreciate the support and prayers they continue to receive from people all over the country". Flake said that McCain has been monitoring what's been going on in Washington closely - "when I visited him last", Flake said, "he had briefing books on his lap, and he was watching the news.
He was diagnosed with glioblastoma last July". Edward Kennedy, D-Massachusetts, and Beau Biden, son of former Vice President Joe Biden. While undergoing chemotherapy and radiation, McCain regularly attended Congress. By December, however, his body had become too weak and he returned to Arizona to continue his treatments and go into physical rehabilitation to try to get his strength.
The statement also included a progress report on McCain's treatment and condition while he's been recovering in his home state.
If McCain were to resign before the end of May, Gov. Doug Ducey, R, would appoint an interim senator and there would be a special election in November.
McCain, who lost the 2008 US presidential election to Barack Obama, is serving his sixth term as a senator.
Meghan McCain, the senator's daughter and a regular cohost on ABC's "The View", tweeted on Monday that her father was as strong as ever.