Sen. John McCain has undergone surgery due to an intestinal infection, his office announced Monday.

A statement said that Republican senator, who has been fighting brain cancer since a diagnosis last year, is hospitalized in a “stable condition,” The Washington Post reports.

McCain, 81, is being treated at the Mayo Clinic in Phoenix, Arizona for an infection linked to diverticulitis, which occurs when pouches form on the walls of the colon.

Last July, McCain was diagnosed with glioblastoma, an intense form of brain cancer that also afflicted the late Senator Edward M. Kennedy and Beau Biden, the son of former vice president Joe Biden. While undergoing chemotherapy and radiation, McCain regularly attended Congress. But since December, the senator has been recovering from the effects of the treatment at his home in Arizona.

McCain’s office issues frequent updates on his health, but it has not said when or if the senator will return to Washington, the Post reports.

His daughter, Meghan McCain, tweeted that her father “continues to inspire me everyday with his intense grit and determination.”

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