Sen. John McCain has completed his first round of radiation and chemotherapy, his daughter announced on Friday.

“My father completed first round radiation/chemo,” Meghan McCain tweeted. “His resilience & strength is incredible. Fight goes on, here’s to small wins.”

The Arizona senator revealed he was diagnosed with glioblastoma, an aggressive type of brain cancer, in July. Medical officials discovered the brain tumor while McCain was undergoing surgery to remove a blood clot from his left eye.

McCain’s office said he would undergo radiation and chemotherapy at the Mayo Clinic in Phoenix while keeping up his work schedule. The 80-year-old senator has said he plans to return to Washington D.C. at the end of Congress’ recess this month.

The senator’s office did not immediately respond to a request for comment.

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Write to Mahita Gajanan at mahita.gajanan@time.com.