"I've worked for two years and I've just been happy, and the good Lord looked after me."
The 'Maggie May' hitmaker, who has been in remission since July, encouraged other men to get checked out for the disease.
Rod - who has eight kids - said: "Guys, you've got to really go to the doctor.
"Finger up the bum, no harm done."
Ronnie, 72 - who has suffered from lung cancer - told him: "Somebody up there likes us, Rod."
Beforehand, Rod had said he was going to "come out" during the evening, and his wife Penny Lancaster said: "Tonight would be a nice night to come out of the closet."
But the singer told the crowd: "No, it's not what you think," before opening up about his prostate cancer battle.
And Prostate Project president Tim Sharp has praised Rod's decision to speak openly about his experiences with the disease.
He said: "Experience has shown what a big difference high-profile celebrities can make when they 'come out' about their cancer.
"Stephen Fry and Bill Turnbull revealing their battles with prostate cancer are a good case in point.
"We have no doubt that Sir Rod's decision to announce his fight with the disease will be equally effective."
- Bang Showbiz
