The "Zoolander 2" actor is now raising awareness of Prostate-Specific Antigen (PSA) Test, reported People magazine.
"If ([my doctor) had waited, as the American Cancer Society recommends, until I was 50, I would not have known I had a growing tumor until two years after I got treated," the star said.
"If he had followed the US Preventive Services Task Force guidelines, I would have never gotten tested at all, and not have known I had cancer until it was way too late to treat successfully," he said.
Stiller was diagnosed with prostate cancer on June 13, 2014. On September 17 of that year he got a test back telling that he was cancer free.
"At first, I didn't know what was going to happen. I was scared. As I learned more about my disease, I was able to wrap my head around the fact that I was incredibly fortunate. Fortunate because my cancer was detected early enough to treat. And also because my internist gave me a test he didn't have to.