By Vy Vo
A History of Survival
Genes may protect patients from dying of colorectal cancer
By Vy Vo
The hereditary link behind certain cancers may seem like a familiar story: A family history of cancer equals increased risk for developing the disease. Women who inherit mutations in the genes BRCA1 or BRCA2 are more likely to develop breast cancer than women who don’t inherit them. Similarly, if a man’s close relative died of prostate cancer, he’s more likely to develop and die of the disease, too.
But researchers know it’s not such a simple story. A study published in the June 4 issue of the Journal of the American Medical Association (JAMA) found some reassuring news for patients with a family history of colorectal cancer: Stage III colon cancer patients with a family history of colorectal cancer had better survival rates than patients without a family history of the disease.
Sound strange? The researchers don’t think so.
“There are some hereditary colon cancer syndromes that are associated with a better prognosis compared with cancer that arises without a family history of cancer,” says Jennifer Chan, a medical oncologist at the Dana-Farber Cancer Institute, in Boston.
According to Chan’s colleague Charles Fuchs, a medical oncologist at Dana-Farber, some previous studies have suggested that genetic changes in colorectal tumors may lead to better outcomes. However, none of these genetic alterations completely account for the survival rates of patients in the study by Chan, Fuchs and their colleagues. This suggests that even more genetic features of colon cancer are yet to be discovered, and that surprisingly, inherited genes may be linked directly to survival.
“We don’t normally think in those terms—that something we are born with actually influences our ability to survive colon cancer,” says Fuchs.
The study tracked 1,087 colon cancer patients undergoing chemotherapy, with 195 of these patients reporting a history of colorectal cancer in a parent or a sibling. Twenty-nine percent of those with a family history experienced cancer recurrence or death during the study, compared with 38 percent of patients without a family history.
The new findings provide even more impetus for research into the genetic basis of colorectal cancer—especially for genome-wide association studies, which survey the entire genetic code to connect genetic alterations to certain diseases or traits, says hematologist-oncologist Boris Pasche, the director of the cancer genetics program at Northwestern University, in Chicago. Researchers have so far pinpointed a genetic cause for 5 percent to 6 percent of colorectal cancer; about 20 percent to 30 percent of colorectal cancer is believed to be inherited. It seems that further examination of inherited colorectal cancer will yield more genetic discoveries, he says.
Pasche’s optimism extends beyond laboratory research and into the lives of patients. Because of the new JAMA study, individuals with a family history of colorectal cancer may be able to breathe a little easier, he says. “These findings provide reassuring news to patients,” Pasche says. “I think it’s a very hopeful message.” Even so, he says patients probably won’t see any immediate changes at their doctor’s offices. That’s because researchers are only slowly discovering the complex effects of these genetic features.
Fuchs agrees. “I don’t know that we are prepared to change clinical practice,” he says.
“For people who already have colon cancer and have a family history,” Chan explains, “we’re still going to be following the standard recommendations regarding chemotherapy.” And, she adds, “for any person who has a family history of colon or rectal cancer, we recommend that they get screening to prevent cancer from developing in the first place.”