Mr. Gannon was fighting the cancer in 2003 when Oz stormed Broadway and became one of the biggest hits of the season, largely based on the audience appeal of star Hugh Jackman, who played entertainer Peter Allen in the musical. Jackman won a Tony Award for his work and became a hot theatre property in process.

"It is a brilliant showcase for somebody because you get to sing, dance and act," Mr. Gannon told the Australian Associated Press at the time, "and because Hugh does all three so brilliantly I think it has shown him in a whole new light in America that people were just not aware of before."

The Boy From Oz was co-produced by Robert Fox and was Gannon's only Broadway credit. Prior to the show, he worked mainly in television and film. One of his projects was a documentary on Allen, who died in 1992 and is a beloved figure in his native Australia. According to the newspaper The Australian, the program led directly to the stage show The Boy From Oz, which debuted in Sydney in 1998 and toured for two years. The show starred Todd McKenney at that time.

The show ran 11 months on Broadway and became something of a phenomenon, despite lackluster reviews. Fans clamored to see the charismatic Jackman, who became famous for his dedication to the part and for never missing a performance. Rather than find a replacement, Mr. Gannon and Fox closed the show when Jackman's contract was up.

In 2005, the show came back to Australia with Jackman as an arena concert. During this time, cancer returned to Mr. Gannon's liver. Mr. Fox told the Australian that Mr.Gannon had given "no murmur of discontent… You would not have known there was anything the matter with him."