Funnyman Ben Stiller is opening up for the first time about a serious health scare that almost ended his life.

During an interview on The Howard Stern Show this morning (October 4), Stiller revealed he was diagnosed with “immediately aggressive” prostate cancer two years ago, at the age of 48.

“It came out of the blue for me,” the Zoolander 2 actor admitted. “The one thing that it does is it just stops everything in your life when you get a diagnosis of cancer, because you can’t plan for a movie, because you don’t know what’s going to happen.”

Stiller had no history of prostate cancer in his family, and he wasn’t considered part of an at-risk group. Even so, his doctor was able to detect the disease by conducting a Prostate-Specific Antigen (PSA) test during his annual physical. The test is controversial in the medical world, Stiller admits, and some health organizations have called it unnecessary. But Stiller says it ended up saving his life, and he’s speaking out about his diagnosis now in the hopes that men will start getting tested younger than the standard age of 50.

“This is a complicated issue, and an evolving one,” Stiller wrote in an essay published on Medium following his Howard Stern appearance. “But in this imperfect world, I believe the best way to determine a course of action for the most treatable, yet deadly cancer, is to detect it early.”

As for how Stiller’s doing now, the actor said he’s been cancer-free for two years, following a procedure to remove his prostate as well as continued PSA tests.

“Afterwards, it just gives you an appreciation for life,” he told Stern. “Every six months I’m taking my PSA test to make sure I’m clear.”

Head here to read Stiller's Medium essay in full.