Alex Trebek says visiting Ottawa always feels like a homecoming.

The longtime host of TV game show Jeopardy! — he's been at the helm since 1984 — was born in Sudbury, Ont., and went to the University of Ottawa. He was back in the city Monday for the official opening of Canada's Centre for Geography and Exploration, the new headquarters of The Royal Canadian Geographical Society, of which he is honorary president.

What's the connection?

Turns out the guy who regularly tosses out answers in need of questions about world geography to Jeopardy! contestants has had a lifelong appreciation of the subject.

"I've always believed that if you know geography, you have a better chance of understanding humanity, because you know why different peoples settled in different areas," he told The National's Rosemary Barton Monday in a sit-down interview at the RCGS.

"You know the development of those countries, you know why boundaries have been established over centuries. And all of that can only work to the benefit of humanity — because if I understand where you're coming from, maybe I'll be nicer to you."

Trebek tells Rosemary Barton he spoke publicly about his cancer to let others living with the disease know that they're not alone. (Philip Ling/CBC News)

Trebek has seen his own fair share of humanity during the past two months. In March, the 78-year-old posted a video to announce he has Stage 4 pancreatic cancer. He had his last chemotherapy treatment this past week and goes in for a PET scan Wednesday.

"Then we'll have a better idea as to where things stand."

According to the Canadian Cancer Society, stage four means the cancer has spread through the blood or lymphatic system to another site in the body.

But Trebek says his pancreatic cancer is a specific mutation that also responds to certain kinds of immunotherapy, which helps boost the patient's own immune system to help fight the disease. He says if the chemo has got rid of any of the tumours, he might be a candidate.

And Trebek hasn't missed a day of work because of the cancer. That doesn't mean he's had an easy go of it. At one point while taping Jeopardy!, he suffered painful stomach spasms. But he toughed it out, he says. "I'm Canadian."

Watch: Alex Trebek talks about how being Canadian has helped him stay tough

Alex Trebek tells The National's Rosemary Barton why even cancer can't force him to call in sick to Jeopardy. 0:44

He's also experienced some depression in the face of the diagnosis, something he's dealt with before.

"Last year … I had a brain surgery for two fairly large blood clots on my brain that were life threatening and that had compressed the brain down quite a bit, and that was frightening. That provided me with a certain amount of depression, because I didn't know what it was."

This time though, he says any feelings of sadness or depression have been different.

"So many people get cancer," he said. "I'm not alone out there. And I want them to feel that they're not alone, that they have somebody who can speak out in public on their behalf and raise their hopes. Because that's so important."

Watch: Alex Trebek talks about why he has to be positive

Alex Trebek talks about why he is so positive and how it ultimately helps him. 0:38

He says he was initially surprised by the extent of support sent his way, too. But no longer.

"There are a lot of really nice people out there," he said. "So it no longer surprises me."

Many of those people — from loyal viewers to celebrities and even the prime minister — have sent messages to Trebek, explaining how the game show host has been such a big part of their lives.

"It has taken me by surprise, the extent to which the show has been a factor in the lives of Canadians and Americans — and by extension, how I also have become a part of their lives," he said. "It's pretty cool."

And though he spoke in that video he released back in March about his prognosis not being great, Trebek also said he was prepared to fight — a message, he explained today, that was as much for himself as for others.

"You've got a choice: You can be pessimistic or you can be optimistic. It's a lot better to be optimistic because you stand a better chance of helping to cure yourself."

Watch Rosemary's full interview with Alex Trebek: