Author and columnist Mark Steyn reacted Monday to Rush Limbaugh's announcement that he has advanced-stage lung cancer and will be off his syndicated radio show until at least Thursday to visit with his physicians.

Steyn, who frequently guest-hosts the "Rush Limbaugh Show," said on "Tucker Carlson Tonight" that he owes a debt of gratitude to the 69-year-old radio legend.

"Unlike many people at the top of this business, Tucker, he has no insecurities, no petty jealousies," said Steyn, who will be filling in for Limbaugh most of this week. "He is secure and kind and generous. Everyone who has had anything to do with 'The Rush Limbaugh Show' will be rooting for him.

RUSH LIMBAUGH ANNOUNCES THAT HE WAS 'ADVANCED LUNG CANCER'

"He is the kindest. I owe him everything. In America, I owe Rush everything."

Steyn said Monday's show was a typical mix of honest conservative insight, humor and random pop culture references. He joked that Limbaugh sounded as at ease as he always does when he made an offhand joke about a song by Welsh singer Tom Jones.

"In the last ten minutes of the show, he told us some really devastating and tough news," said Steyn, who added that the news was shocking coming from Limbaugh, who he described as an upbeat, kind man who has had a "rich life."

Steyn added that Limbaugh, who has been broadcast nationwide since 1988, is remarkable in the way he has been able to keep his program at the top of the ratings for decades despite having nearly no guests. He recalled a visit to Australia where he had to tell then-Prime Minister John Howard that he had to fly back to the U.S. to guest-host Limbaugh's show for the first time. Howard remarked to Steyn how large the radio legend's following was.

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"I said 'Yes, about 25 to 30 million listeners'. [Howard] goes, 'Rush has more listeners than we have Australians'."

Earlier Monday, Sean Hannity credited Limbaugh with helping him build his prominence in the radio industry by allowing him to guest-host in the 1990s.

Since then, Limbaugh has welcomed a handful of commentators and regional AM radio hosts to helm the show while he is away, most recently including Steyn and Harrisburg, Pa. talk show host Ken Matthews.