Twenty-one years ago my mother, Mary Lewis, learned that she had cancer. It was skin cancer — melanoma — doctors told her, and by the time it was detected, the cancer had already spread to her lymph nodes. She was given six months to live, but even as the cancer ravaged her body, she held on for two years. She died at a hospice in 1993. She was 56.

Four years ago my oldest brother, Joe, sat me down in the living room of his home and explained to me the seriousness of his cancer. It was prostate cancer, and by that time it had spread to his lymph nodes, too. He explained that even though the drugs he was taking would buy him some time, the cancer cells would eventually consume his body. Our family was at Joe’s hospital bedside the night he died in April 2010. He left behind a wife and four sons — two of them in their early teens.

One family. Two devastating results. And now cancer’s back for a third round. This time it’s my battle. What I expected to be a routine PSA (prostate-specific antigen) blood test last year resulted in a call from my doctor that felt like a sledgehammer to the head: “Your levels are elevated,” she told me. “We want you to come in and get retested.”

The second test also came back elevated. The biopsy that followed confirmed the worst: I had cancer. Damn.

Even though it’s been some time since I was told that I had cancer, I’m still numb. To know that something inside my body can potentially kill me consumes my thoughts every day. The thought of what cancer has done to my family — and what it can do to me — robs me of sleep every night. Still, I consider myself lucky.

Prostate cancer is a silent killer, and because it grows slowly, many men have no idea it’s there. With the spike in my PSA levels, it’s likely that I’ve lived with cancer for many years. Fortunately for me, the cancer was found in its early stages and, based on tests so far, never left the prostate. Doctors tell me that with treatment, I can expect a full recovery.

But some men never have a shot at recovery, mainly because they have no idea the cancer is there. After telling a close friend two weeks ago that I had prostate cancer, I asked him the question that I ask all my friends now: When was the last time you had a PSA test? His response: Never. He’s 49 years old, just like me.

The following facts — which I learned after I was diagnosed — will, hopefully, have him calling his doctor this week:

One in six men will be diagnosed with prostate cancer during their lifetime. Think about that: If you’re at home having a cookout with 11 of your buddies, it’s likely that two of you at some point in your lives will be diagnosed with prostate cancer.

If you’re an African-American man, those odds increase to nearly one in five. African-American men have the highest rate of prostate cancer in the world and have the disease at rates three times higher than those of white men.

Prostate cancer is the second-most-common cancer among men, behind skin cancer, and the second leading cause of cancer deaths among men.

If a first-degree family member has prostate cancer (like my brother), you have nearly three times the risk of being diagnosed.

The average age of diagnosis is 65. But I’m proof that, while not the norm, the disease also occurs in younger men. I was diagnosed at 49, but the cancer may have been growing inside me since my first PSA spike, when I was 45. St. John’s basketball coach Steve Lavin was 46 when he was diagnosed, and dealing with the disease took him out of last season.