TUESDAY, June 3 (HealthDay News) -- The genetic makeup that increases the risk of developing colorectal cancer also seems to improve the chances of survival after treatment, a new study indicates.

People with colorectal cancer who had close relatives with the malignancy were 28 percent less likely to die or to have a recurrence after treatment, according to a report in the June 4 issue of the Journal of the American Medical Association by physicians at the Dana-Farber Cancer Institute in Boston.

It is well-known that a close relative of someone with colon cancer is more likely to develop such a cancer, "which is why we recommend that patients who have a family history of colorectal cancer get routinely screened," said study author Dr. Jennifer A. Chan, an instructor in medicine at Harvard Medical School and Dana-Farber. "That is why we did this study."

The study included 1,087 people who had undergone surgery for their cancers and began drug therapy. Over an median follow-up period of 5.6 years, 29 percent of those with a family history died or had a recurrence of cancer, compared to 38 percent of those without a family history.

The reason for the difference isn't known or understood, Chan said. The researchers did try to determine whether lifestyle factors such as diet might be the reason but found no connection.

"Our study was not able to determine the cause," she said. "What we suspect is that there might be some sort of genetic trait that not only increases the risk, but also improves the prognosis for cancer patients."

The increase in survival was associated with the strength of the family history. Participants with two or more close relatives with the cancer had a 51 percent lower risk for cancer recurrence or death than those with no family history.

The immediate impact of the discovery might be to give some reassurance to people with colorectal cancer and a family history, Chan said. "What we hope is that this observation leads to further studies to understand the biological reasons," she said. "If we understand those reasons, we might be able to make better treatment decisions."

The study "could change some expectations about colorectal cancer," said Dr. Boris Pasche, director of the cancer genetics program at Northwestern University, who wrote an accompanying editorial.

"The genetics of colorectal cancer are very clear," Pasche said. "There is an increased risk for those with a family history. But we still don't know what is causing that inheritance."

On the clinical level, the study indicates that "patients with a family history of colorectal cancer might be more treatable than whose who do not," Pasche said.

"If these intriguing findings are validated in other studies, family history may well become a new prognostic factor in colorectal cancer," he wrote. "Should this be the case, genome-wide association studies and tumor gene expression profiling studies will be warranted."

More information

Learn about colorectal cancer from the U.S. National Library of Medicine.