Now, researchers have further clarified that risk.
They found that men who have a first-degree relative (father, brother or son) with prostate cancer have a 2.5 times greater risk of getting the cancer, compared with the general population.
What's more, having a brother with the disease raises the risk more than having a father with it, says Dr. Harry Ostrer, a professor of pediatrics, pathology and medicine at the New York University School of Medicine.
Men who had brothers with prostate cancer are 3.3 times more likely to get the disease than the general population, while those whose father has been diagnosed have a 2.1 times greater risk of getting the cancer.
Exactly why having a brother with the disease boosts a man's risk more than having a father with it is not known. "But it is possibly due to shared genes or environmental exposure," Ostrer says.
Ostrer is a co-author of the analysis, published in the April 1 online edition of Cancer. The analysis was based on a review of 33 previously published studies.
The study also found that having a second-degree relative (uncle, grandparent, cousin) boosted the risk of getting prostate cancer by 1.6 times, compared with the general population.
The researchers also discovered that the greater the number of first-degree relatives with prostate cancer, the greater the risk of getting the disease. And, the younger the age at which a family member is diagnosed, the greater the risk for other family members.
For example, the risk for men whose first-degree relative is under 65 at diagnosis is 2.4 times greater than the general population, but just 1.7 times greater for those whose relative is older than 65.
In the United States, prostate cancer is the most common malignancy among men, not counting skin cancers. This year, 220,900 men are expected to receive a diagnosis of prostate cancer, according to American Cancer Society projections, and 28,900 deaths are expected.
The walnut-sized gland, located in front of the rectum and beneath the bladder, contains gland cells that produce some of the seminal fluid. This fluid nourishes sperm cells in semen.
Besides family history, other risk factors for prostate cancer include advancing age, with 70 the average age at diagnosis. Blacks are more likely than whites to contract the disease, and it is less common in Asians and Native Americans.
Dr. Durado Brooks, director of prostate and colorectal cancer for the American Cancer Society, praises the new analysis. "I think it was time well invested," he says.
"Most studies have found a two to four times greater risk" among men with a family history, Brooks says. So, the new analysis has quantified that risk more clearly, he adds.
The report may help men decide when and if to go for screening, Brooks says. Men who know they are at higher risk than the general population may decide to undergo screening tests earlier.
Currently, the American Cancer Society suggests that men at average risk discuss the benefits of screening with their doctor and make an informed decision, Brooks says. Men at average risk should talk about beginning screening at age 50; those at high risk at age 45, he adds.
Screening includes a digital rectal exam and a blood test to detect prostate-specific antigen, a substance that may rise in the presence of prostate cancer.