It kills four men every day in London - 1,600 every year.
Many of them die because of embarrassment, ignorance or fear.
We're talking about prostate cancer and today ITV - in conjunction with Prostate Cancer UK - has launched "Stand By Your Man".
It's a campaign to raise awareness of the disease - to encourage men to talk about their health
Above all, it's to help save lives.
Nick Thatcher's report contains explicit descriptions about prostate cancer symptoms.
More than 40,000 men are diagnosed with prostate cancer in the UK every year, yet few get themselves tested. Here's what you need to know.
Actor Neil Stuke, who stars alongside Ray Winstone and Tamzin Outhwaite in a new film about prostate cancer, writes about the disease.