"My oncologist tells me I'm doing well, even though I don't always feel it," Trebek said.
"I've had kidney stones, I've had ruptured disks, so I'm used to dealing with pain. What I'm not used to dealing with is these surges that come on suddenly of deep, deep sadness."
"I'm fighting through it," he told Roberts.
"My platelets, my blood counts are steady, my weight is steady. The cancer indicators are coming down. So I've got another chemo next week and then we'll do a review to find out where things stand."
Trebek plans to "recuperate and get strong again" over the summer before returning to "Jeopardy!" in the fall.
"Hopefully everything is going to turn out well and I'll be back on the air with original programming come this September," he said.
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The "Jeopardy!" host thanked fans and other cancer survivors for their support since his diagnosis.
"It's great to be considered an inspiration to other people," Trebek said.
"People all over America have been sharing their good thoughts, their advice, their prayers, and I feel it is making a difference in my well-being."
"I've had so many contacts from people who have survived cancer for 10 years, 12 years, 14 years. I am now a 30-day cancer survivor," he added. "They have been an inspiration to me, and that's really what's it's all about -- it's growing attention to this particular type of devastating cancer."
Trebek went public with his diagnosis in a video message in March.
He said on Twitter in April he is "feeling good" and planning to host the new season of "Jeopardy!" in the fall.
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