Alex Trebek undergoing more chemotherapy after 'Jeopardy!' return

Roughly a week after he triumphantly returned to "Jeopardy!," Alex Trebek revealed he's undergoing another round of chemotherapy to treat his pancreatic cancer.

Trebek, 79, said in an interview published Tuesday his doctors think more chemotherapy is warranted after his "numbers went sky high" and he lost 12 pounds in just a week.

“I was doing so well," the beloved host told ABC News. "My numbers went down to the equivalent of a normal human being who does not have pancreatic cancer. So we were all very optimistic. And they said, 'Good, we're gonna stop chemo, we'll start you on immunotherapy.'"

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But soon after, his doctors decided Trebek needed to undergo more chemotherapy — "and that's what I'm doing," he said.

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Trebek revealed in March he was diagnosed with stage 4 pancreatic cancer, and he underwent treatment before returning to the famed game show. He told ABC that when he was first diagnosed, he "was down on myself."

“I didn’t realize how fallible each of us is in his or her own way … I talk to the audience sometimes and I get teary-eyed for no reason. I don’t even bother to explain it anymore, I just experience it," Trebek said. "I know it's a part of who I am and I just keep going.”

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He described cancer as "mysterious in more ways than one" and detailed "excruciating pain" and "fatigue" he feels while battling cancer.

On Sept. 9, however, he returned to "Jeopardy!" for the show's 36th season.

Trebek previously revealed that he cried “happy tears” when he learned that the treatment was working after struggling with it for weeks. He noted that he believes he has a distinct edge over the average person battling the disease.

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“I’ve got a couple million people out there who have expressed their good thoughts, their positive energy directed toward me and their prayers,” Trebek shared. “I told the doctors, this has to be more than just the chemo, and they agreed it could very well be an important part of this.”

Fox News' Jessica Sager contributed to this report.