People with a family history of colon cancer carry the emotional burden of knowing that they have twice the risk of developing the disease themselves. But a new study might ease some of their anxiety. Patients with a family history of colon cancer, the researchers found, are also more likely to survive it.
The paradox, being published today in The Journal of the American Medical Association, could steer researchers toward new treatments and a better understanding of the disease.
An estimated 153,000 cases of colon and rectal cancer will be diagnosed in the United States in 2008, according to the American Cancer Society, and about 50,000 people will die of it. Studies of twins show that about 35 percent of colon cancers are inherited, and about 11 percent of patients have at least two close relatives with the disease.
Someone who has a parent or a sibling with colorectal cancer faces about a 1-in-10 chance of developing colon cancer, compared with a 1-in-20 chance for those with no family history of the disease.
The study, conducted by researchers at the Dana-Farber Cancer Institute in Boston, followed 1,087 patients being treated for Stage 3 colon cancer, which means it had spread to nearby lymph nodes but not to other organs. Of those patients, 195, or about 18 percent, had a parent or sibling with the disease. Those who had at least one such close relative with colon cancer were 25 percent less likely to die of the disease during the 5.6 years of patient follow-up than those with none.
The risk of dying was even lower for those with two or more relatives with the disease. Those patients had a 51 percent lower risk of recurrence or death.
"This news may be reassuring to people with a family history, but our hope is that we can discover what underlies this effect of family history in biological terms," said the study's first author, Dr. Jennifer Chan of the Center for Gastrointestinal Oncology at Dana-Farber.
Why a person with a family history of colon cancer has a better prognosis is not clear. The scientists ruled out several explanations for the difference, including the possibility that people with a family risk have adopted healthier lifestyles or take part in added screening.
Chan said the researchers looked at lifestyle factors such as diet, exercise and smoking, and had found no association with improved survival.
The study was financed by grants from the National Cancer Institute and the Pharmacia & Upjohn Co., now Pfizer Oncology.