​Sen. John McCain was returning to Arizona on Sunday and will skip this week's vote on the Republican tax bill, according to several reports.

“I wish John well. They’ve headed back [to Arizona]," President Donald Trump told reporters Sunday after returning from a weekend at Camp David. "But I understand he’ll come if we ever needed his vote, which hopefully we won’t."

According to CNN, sources close to McCain say it is unlikely the Arizona Republican will return to Washington this year. CBS News also reported that the senator will not vote on the tax bill.

Senate Republicans are believed to have enough votes to pass the tax bill without McCain. A vote could come as soon as Tuesday

McCain was hospitalized at Walter Reed Medical Center in Bethesda, Md., for most of the last week, recovering from the side effects of chemotherapy for brain cancer.

The senator's daughter Meghan McCain tweeted Sunday that the McCain family was "looking forward to spending Christmas together in Arizona."

McCain and his family requested that The National Institutes of Health's National Cancer Institute release a statement about the senator's treatment Sunday:

“Senator McCain 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.”

Here in Arizona, there has been intense speculation that McCain would retire from the Senate this week, after the tax bill vote.

But a statement from McCain's office said he would be returning to Washington in January:

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.

Under Arizona law, Gov. Doug Ducey would appoint a replacement.

McCain, who is 81, was diagnosed with a glioblastoma -- a cancerous brain tumor -- last July.

Glioblastoma is the same aggressive cancer that killed Sen. Edward Kennedy and Beau Biden, the son of former vice president Joe Biden. The cancer has a median survival rate of 14 months.

Meghan McCain's marriage to conservative writer Ben Domenech was pushed up to last Thanksgiving weekend because of her father's declining health.

"It’s a deeply unpredictable cancer. You’re really just living scan to scan," Meghan McCain told People magazine after the wedding.

RELATED: 'Your dad took care of my Beau': Joe Biden consoles Meghan McCain on dad's cancer

On Friday, President Donald Trump reportedly phoned Cindy McCain, the senator’s wife, to check on McCain’s health and wish him well.

Sunday, returning from Camp David, Trump answered questions from reporters and said McCain would head back to Washington if the Republicans needed his vote for the tax bill.