Sen. John McCain will not be in Washington when Congress votes on the Republican tax bill this week, CNN reported Sunday.

The Arizona Republican returned to his home state Sunday to continue recovering from the side effects of chemotherapy for a brain tumor, two sources confirmed to CNN. The senator’s daughter, Meghan McCain, confirmed in a tweet that her father would be in Arizona for Christmas.

“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,” she tweeted Sunday afternoon.

McCain, 81, is unlikely to return to Washington this year, one of the sources told CNN. The senator left Walter Reed Medical Center “exhausted, but OK,” a Republican close to him said.

Dr. Mark Gilbert, chief of neuro-oncology at the National Institutes of Health's National Cancer Institute, released a statement Sunday saying McCain “continues to improve” after being treated for a viral infection. He added the senator is also responding positively to his ongoing cancer treatment.

McCain's office released a statement Sunday night: "Senator McCain has returned to Arizona and will undergo physical therapy and rehabilitation at Mayo Clinic. He is grateful for the excellent care he continues to receive, and appreciates the outpouring of support from people all over the country. He looks forward to returning to Washington in January."

McCain was admitted into the hospital on Wednesday after missing a third straight day of votes in the Senate.

The final vote on the Republican tax bill is expected to take place early this week.

The passage of the tax bill, however, does not hinge on McCain's support because the GOP has a 52-48 vote advantage in the Senate. Vice President Mike Pence can also cast a tie-breaking vote, should it be needed.