Prostate cancer

The rock legend made the revelation at a fundraising event on Saturday.

"No-one knows this, but I thought this was about time I told everybody. I'm in the clear, now, simply because I caught it early. I have so many tests," he said, according to The Mirror.

The 74-year-old was speaking at an event for the Prostate Project and golf's European Tour Foundation.

He joked to wife Penny Lancaster that he was going to use the evening to "come out", adding: "It's not what you think. Two years ago I was ­diagnosed with prostate cancer."

The test detects cancer DNA in the blood, helping doctors check whether precision drugs are working.

Cancer Research UK said the test could "greatly improve survival".

But larger studies involving more men needed to take place to confirm if doctors could rely on the test, the charity said.

Blood samples from 49 men with advanced prostate cancer were collected by researchers, as part of the phase II clinical trial of a drug called olaparib.

The approach, tested across Europe, uses lasers and a drug made from deep sea bacteria to eliminate tumors, but without causing severe side effects.

Trials on 413 men - published in The Lancet Oncology - showed nearly half of them had no remaining trace of cancer.

Lifelong impotence and incontinence are often the price of treating prostate cancer with surgery or radiotherapy.

Up to nine-in-10 patients develop erectile problems and up to a fifth struggle to control their bladders.

The star of Zoolander was diagnosed with a tumour in 2014.

He says he now wants to share his story to lend his support for a controversial test which saved his life.

In an article on Medium, Stiller described the moment of his diagnosis as "a classic Walter White moment, except I was me, and no-one was filming anything at all".

He wrote: "I got diagnosed with prostate cancer Friday, June 13 2014. On September 17 of that year I got a test back telling me I was cancer free.