Republican Sen. John McCain left Washington, D.C., Sunday to be with his family in Arizona, and will miss the vote on the Tax Cuts and Jobs Act expected this week, CBS News reports.

McCain, 81, spent a most of the week at Walter Reed National Military Medical Center in Bethesda, Md., following a routine chemotherapy treatment for brain cancer, but is doing well and is in “good spirits,” McCain’s son-in-law, Ben Domenech, told CBS’ Face The Nation Sunday.

“I’m happy to say that he’s doing well,” Domenech, publisher and founder of The Federalist, told CBS. “The truth is that as anyone knows whose family has battled cancer or any significant disease that oftentimes there are side effects of treatment that you have.”

“The senator has been through a round of chemo and he was hospitalized this week at Walter Reed,” Domenech added.

The GOP has a slight majority with 52 Republican senators, and with McCain’s absence will only be able to afford one dissenting vote. Vice President Mike Pence recently postponed a trip to Israel scheduled for the coming week in order to be available to cast a tie-breaking vote in the Senate, if needed.

The already narrow margin for the tax reform bill is exacerbated by concerns for McCain’s health, and the health of another member, GOP Sen. Thad Cochran of Mississippi. Cochran had “an outpatient procedure Monday afternoon to address a non-Melanoma lesion on his nose,” but his office said it expects him to be available for the tax vote.

GOP Sen. Lindsey Graham of South Carolina said earlier this week that he’s “not focused on the tax bill right now when it comes to Sen. McCain. I’m focused on his health.”

The Senate passed the initial tax bill Dec. 2 with 51 votes after Tennessee GOP Sen. Bob Corker dissented. Corker said earlier this week that he would support the final version of the bill, that has been rewritten in conference with House and Senate members.

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