Doctors don't know why one man develops prostate cancer and another doesn't.

But there are certain risk factors that make it more likely in some people, the U.S. National Cancer Institute says.

These include:

• Age. Men under age 45 rarely get this disease, while most men who do are over age 65.
• Family history. Your risk of contracting prostate cancer is higher if your father or brother had it.
• Race. Black men have a higher incidence of prostate cancer than white men; Asian and Native American men appear to be at lower risk.
• A diet high in animal fat.
• Certain cell changes in the prostate.

It's important to note that most men diagnosed with prostate cancer don't have any risk factors, except growing older, the institute says.