Family history is known to be a risk factor in many diseases, including prostate cancer. Yet many men aren't aware of the increased risk they face if they have relatives with the disease.

A recent study published in the journal Cancer (Vol. 97, No. 8: 1894-1903) could be a wake-up call. Researchers from New York University and Maastricht University in the Netherlands analyzed 33 previous studies of family history and prostate cancer to help clarify the risk men in this situation face. The studies involved more than 200,000 patients.

The analysis confirmed that a man who has a father or brother with prostate cancer has more than double the risk of developing the disease himself, compared to a man with no family history of the disease. Men who have two or more relatives with prostate cancer have about five times the risk.

The researchers also found that the risk is generally higher for men with affected brothers than for those with affected fathers, and that the risk is higher for those with relatives diagnosed at younger ages.

"A significant number of men who have a family history don't know that means they're at markedly increased risk," said Durado Brooks, MD, director of prostate and colorectal cancer for the American Cancer Society. "Men are aware that prostate cancer is a significant issue in general, but they often don't relate that general health issue to their own personal health," he added.

But even when men do understand their risk, they may not be taking appropriate measures to prevent prostate cancer or detect it early.

Another recent study, published in The Journal of Urology (Vol. 169, No. 5: 1715-1719), examined prostate cancer screening trends in 138 brothers and sons of prostate cancer patients between the ages of 40 and 70.

Doctors at the University of California-Los Angeles found that even though 75% of the men knew that having a father or brother with the disease increased their risk of getting it, only 62% had been screened for prostate cancer with the prostate-specific antigen (PSA) blood test and a digital rectal examination in the past two years.

The numbers highlight a "disconnect" between what men know about their health, and what they do to protect it, said study coauthor Mark S. Litwin, MD, a professor of urology and public health and a researcher at the Jonsson Comprehensive Cancer Center at UCLA. It also points to a challenge for the public health community.

"Seventy-five percent are aware (of their higher risk)," he said, "so we've done a good job imparting knowledge, but we haven't done as good a job of getting men to act on that knowledge."

When the researchers examined factors that influenced whether men got screened, one stood out: the influence of doctors.

Men who discussed prostate cancer screening with their doctors were 18 times more likely to get a PSA blood test and digital rectal examination than men who did not talk to their doctors about screening.

Since all these men were at higher than average risk for prostate cancer, why wasn't screening part of their health care conversations? There are several possible reasons. Doctors may be unaware of a patient's family history of prostate cancer. Or they may not realize how much greater the risk is for men with a family history of the disease.

Litwin and his colleagues offer another possible explanation: the controversy within the medical community over prostate cancer screening. Although the PSA blood test and a digital rectal exam can help detect prostate cancers while they are at an early stage, doctors are not sure how much that benefits patients.

Prostate cancer grows very slowly, so in some men the cancer would never cause symptoms or problems. Treating the cancer, however, can have serious side effects like incontinence and impotence. Unfortunately, doctors have no way to determine which men have more aggressive cancers that do need treatment, and which men do not.

The American Cancer Society recommends that men at high risk for prostate cancer, such as African Americans and those with a history of the disease in a father or brother, begin testing with both the PSA blood test and the digital rectal exam at age 45, or even younger if they have multiple relatives with the disease. Men at average risk should be offered testing beginning at age 50, if they have a life expectancy of at least 10 years. The guidelines also say all men should be advised of the potential benefits and risks of early detection and treatment of prostate cancer.

"We feel providers should be talking with all their patients about benefits and limitations, and in particular they need to talk with patients at increased risk and let them know they stand a greater chance of having a benefit from screening," Brooks said.

Litwin agreed. "If there's any consensus, it's that men who are at high risk ought to seriously consider being screened," he said.

But patients need to take initiative, too, both Brooks and Litwin said. Men should ask their doctors about what types of screening might be appropriate for them. And those who already have prostate cancer should talk to their brothers and sons about the risk that runs in families.

Doctors can encourage this type of communication, Litwin said, by being sure their prostate cancer patients are informed of family risk and the importance of screening. "Primary care physicians and prostate cancer specialists need to be sure and counsel their prostate cancer patients to talk to their own brothers and sons," he said.

But the burden rests mainly with each man himself.

"The physician's job is to counsel the patient, but ultimately it's up to the patient," Litwin said.