Arizona Sen. John McCain has completed his first round of radiation and chemotherapy treatment, his daughter revealed on Friday afternoon.

Meghan McCain tweeted the update and said her father's resilience and strength is incredible.

"Fight goes on, here's to small wins," she added.

Last month, Sen. McCain was diagnosed with a brain cancer called glioblastoma and had a tumor removed. He briefly returned to Washington D.C. for the vote on the Republican's health care bill. His vote wound up being critical in stopping the repeal of Obamacare.

Since then, McCain returned to Arizona for more treatment for the cancer at the Mayo Clinic.

Meghan McCain tweeted Friday that her father has completed his first round of radiation and chemotherapy treatment. 

McCain tweeted a photo thanking his doctors on Friday.