People with a family history of colon cancer carry the emotional burden of knowing they have twice the risk of developing the disease themselves. But now, a new study may ease some of their anxiety. Patients with a family history of` colon cancer are also more likely to survive the disease.
The surprising paradox, published in Wednesday’s Journal of the American Medical Association, may ultimately 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 2008, according to the American Cancer Society, and about 50,000 people will die from the disease. 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. An individual who has a first-degree relative with colorectal cancer faces about a 1 in 10 chance of being diagnosed with colon cancer, compared to 1 in 20 for those with no family history.
The latest study, conducted by researchers at the Dana-Farber Cancer Institute in Boston, followed 1,087 patients being treated for Stage III colon cancer, which means the cancer 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 close family member with colon cancer were 25 percent less likely to die from the disease during the 5.6 years of patient follow-up than those with no close relatives with colon cancer.
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 for cancer 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, from Dana-Farber’s Center for Gastrointestinal Oncology.
Why a person has a better prognosis if they have a family history of colon cancer isn’t clear. The scientists ruled out several explanations for the difference, including the possibility that people with a family risk for colon cancer have adopted healthier lifestyles or take part in additional screening. Dr. Chan said the researchers looked at important lifestyle factors like diet, exercise and smoking and found no association with improved survival. And because all the patients had stage III cancers, more frequent screening and an earlier diagnosis also couldn’t explain the difference.
However, there is other evidence that genetic factors play an important role in colon cancer prognosis. It’s known, for example, that colon cancer that develops as a result of a rare inherited condition called Lynch syndrome — also called hereditary nonpolyposis colorectal cancer — is less aggressive than the cancers found in patients with no genetic risk.
The study was paid for with grants from the National Cancer Institute and Pharmacia & Upjohn Co., now Pfizer Oncology.
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