PORTLAND, Oregon — One day in Chicago, Dave Bigg is about to drink a few beers with his buddies and divvy up Cubs baseball tickets when his cell phone rings. It’s the doctor. Mr. Bigg’s biopsy looks bad. The cells from his prostate are warped and buckled. It’s cancer.

Mr. Bigg can’t believe what he’s hearing. He’s 46 years old. He doesn’t look sick. He doesn’t feel sick. Hell, he feels great — he’s training for a triathlon. “It was like a punch in the stomach,” Mr. Bigg recalls.

This year, more than 230,000 men in America will get bad news, according to the American Cancer Society. And these men will face difficult choices about what to do next. Out of the blue, a diagnosis of prostate cancer will throw them into the middle of a raging medical debate over how to treat this disease — or whether to treat it at all.

For some, the decisions they make will determine whether they live or die. For others, their choices will mean the difference between an active sex life and impotence.

One man in six in America will be diagnosed with prostate cancer during his lifetime, the ACS says. After age 40, the danger grows with each passing year. If you live long enough, the question becomes when, not if, you are likely to get this cancer. Autopsies show that 30% of American men over 50 have at least some malignant cells in the gland. For men older than 80, that figure climbs to 80%, according to the ACS.

Prostate cancer kills one in 34 men in America. Virulent tumors often spread to the bone. More than 27,000 America men are likely to die from prostate cancer this year, the ACS says. This form of cancer is more common in men than any other cancer aside from that of the skin. It is more prevalent than cancer of the lung, which strikes one man in 13; of the colon, which hits one in 17; or of the bladder, which besets one in 28, according to the National Cancer Institute.