While performing at an event in aid of prostate cancer last month, the Maggie May singer revealed he had secretly battled the illness for two years before being given the all clear.
In an emotional appearance on Loose Women, Lancaster spoke about her spouse's illness where she reflected on how "aggressive" the disease had been.
She shared with the panellists: "It was [quite aggressive]. It came on really quickly. With Rod it was an aggressive one. It left the gland and travelled to the outside tissues.
"So that was another scary moment where we had to have more invasive tests and scans to see if it was anywhere else secondary in his body, which was the most frightening test of all. But it hadn’t gone.”
Becoming visibly overwhelmed, Lancaster went on: “It’s emotional. We kept it quiet for two and a half years now. The positive news is we caught it early enough.”
Lancaster also opened up on the radiation treatment Stewart underwent before he was free of the cancer.
She said: “Rod and I were travelling into London at the same time every single day, going to the clinic. Rod’s never done one day, one week the same ever in his entire life. He put his positive head on, along with myself.
"The nurses had a little room for him. He took his computer, he said this was like my day in the office.”
Stewart himself sent a message into the show where he urged others to get their prostate examined.
“I’ve just been given the OK. Guys, please, get down to the doctors and get tested - it’s a rotten disease… Finger up the bum, no harm done," he said.