TUESDAY, July 12 (HealthDay News) -- Family history remains one of the best ways to identify people at high risk for breast, prostate and colon cancer, and now new research suggests that updating your doctor between ages 30 and 50 about any close relatives who develop these cancers may lead to lifesaving changes in how and when you are screened.

"Family history is very important, and it can give [individuals] a sense of whether they are at elevated risk for certain types of cancers, and this could impact how they are screened," said study author Dianne M. Finkelstein, of the Massachusetts General Hospital Biostatistics Center in Boston.

Details matter, Finkelstein said. "If anyone in your family gets cancer, you should know the age when they were diagnosed and the original site of the cancer," she said.

"Let's say you are 35, and there is no one with cancer in your family and then you go back to your doctor, and your older brother is diagnosed with colon cancer," she said. "This information changes the doctor's strategy with respect to colon cancer screening and they may find any cancer earlier, which may change the outcome." (Having a close relative with colon cancer increases the risk 2-fold to 6-fold, she and the other researchers noted.)

In the future, family history should become a routine part of the intake process, Finkelstein said.

For the study, reported in the July 13 issue of the Journal of the American Medical Association, the researchers analyzed data on adults with a personal or family history of cancer or both who were part of a cancer registry called the Cancer Genetics Network. Changes in self-reported family history of cancer occur throughout adulthood, and this increases steeply before the age of 50 for breast and colorectal cancer, and before the age of 60 for prostate cancer.

Specifically, the recommendations for high-risk screening -- based on changes in family history of cancer -- increased by 1.5-fold to 3-fold for colorectal and breast cancer among adults between 30 to 50 years old. The change was less dramatic in regard to prostate cancer.

"We need to concentrate on updating our information with regard to family history," said Dr. Stephanie Bernik, chief of surgical oncology at Lenox Hill Hospital in New York City. "This information can influence screening schedules for certain cancers," she said. "There are drugs that we can offer high-risk individuals to reduce their risk, so it's important for patients to know their status."

Dr. Robert Smith, director of the cancer screening national office of the American Cancer Society, said that "the public needs to understand that family history is important and good communication with first- and second-degree relatives is essential," he said.

The onus also falls on the physician to ask about family history, Smith said. "They should update this information every time they see the patient and make it clear that if there is a change, it needs to be reported."

Knowing about it is one thing, acting on it is another, he added. "Sometimes the information isn't collected or collected thoroughly enough," he says. "Primary-care physicians have to get to a point where they recognize certain family history as high risk and send patients to a genetics specialist," he said. "Gains in genetic medicine are not worth as much as they might be if people don't act on this information."

More information

For more information about cancer and its risk factors, visit the American Cancer Society.