The 81-year-old senator, who was admitted to the Walter Reed Medical Center in Maryland on Wednesday, was returning home from Washington, D.C., on Sunday, CBS News reported.
McCain (R-Ariz.) will not attend the GOP's tax bill vote that is expected to take place sometime early this week. The bill has the support of Republican Sens. Bob Corker of Tennessee and Marco Rubio of Florida. Both pols originally opposed the Senate's plan.
Dr. Mark Gilbert, McCain's doctor, released a statement Sunday saying the senator "has responded well to treatment he received at Walter Reed Medical Center for a viral infection and continues to improve."
"An evaluation of his underlying cancer shows he is responding positively to ongoing treatment," Gilbert added.

"Thank you to everyone for their kind words. My father is doing well and we are all looking forward to spending Christmas together in Arizona," the senator's daughter, Meghan McCain, tweeted Sunday.
McCain underwent surgery in mid-July to remove a blood clot from his left eye after being diagnosed with an aggressive tumor called glioblastoma.
The former Vietnam War veteran had been going through radiation and chemotherapy treatments.
Comment: Aw, poor McCain is gonna miss the vote. Couldn't happen to a nicer person.
But seriously dude, you've got BRAIN CANCER. Maybe it's time to retire? There's enough evil in Washington that calling it a day probably isn't going to be noticed. Plus it would be a convenient time for you to exit the scene given that the Trump dossier scandal is edging closer to implicating your involvement. And we hear the stress is getting to you.
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