Sen. John McCain opened up Sunday about the moment he was diagnosed with an aggressive, often deadly form of brain cancer earlier this year.

In a forthcoming interview on CBS’ 60 Minutes, the Arizona senator spoke about what it was like when doctors told him he had glioblastoma, an aggressive form of brain cancer. At the time, McCain was visiting his doctor at the Mayo Clinic in Phoenix to check out a blood clot in his eye.

“As you know, doctors are interesting,” he told CBS, adding that he repeatedly told his doctors to “tell it to me straight.”

It was only days after the operation that doctors confirmed the results via labs. They told McCain that his prognosis was not bright.

“Some say 3 percent, some say 14 percent. You know it’s—it’s a very poor prognosis,” he told CBS. “So I just said, ‘I understand. Now we’re going to do what we can, get the best doctors we can find and do the best we can, and at the same time celebrate with gratitude a life well lived.'”

Since his diagnosis earlier this summer, McCain has already completed his first round of chemotherapy treatment.

And despite the unexpected cancer diagnosis, McCain returned to work at the Senate shortly after he recovered from the surgery for his blood clot — casting the deciding vote that ended a previous attempt by Republican senators to repeal and replace Obamacare in July.

And earlier this week, he once again came out against the latest GOP health care repeal plan, dubbed the Graham-Cassidy bill.

“I cannot in good conscience vote for the Graham-Cassidy proposal,” McCain said in a statement. “I believe we could do better working together, Republicans and Democrats, and have not really tried. Nor could I support it without knowing how much it will cost, how it will effect insurance premiums, and how many people will be helped or hurt by it.