NEW YORK (Reuters Health) Jul 16 - People who have had colon cancer are more likely to be diagnosed with another cancer than those with no history of the disease, a new study suggests.
Using registry data from nine states, researchers found small intestine, lung, kidney, stomach, bladder and endometrial cancers were all more common among people with a history of colon cancer.
The new study included about 170,000 people diagnosed with those cancers between 1992 and 2009. During that span, 15,000 (about 9%) were found to have a second cancer.
Compared to the average American, who according to the American Cancer Society has a lifetime colon cancer risk of 5%, people in the study with a history of colon cancer were twice as likely to develop a second colon cancer.
Colon cancer survivors were 42% more likely to be diagnosed with kidney cancer (i.e., the lifetime risk went from about 1.6% to about 2.3%), the researchers found.
The colon cancer patients were also 14% more likely to get lung cancer compared to the average American, for whom, according to the ACS, the lifetime risk is about 8% in men and 6% in women.
Those risks varied by where in the colon or rectum the first tumor was found, according to findings published July 15 in Cancer.
"We saw the greatest increased risk among individuals whose first cancer was located in sort of the central portions of the colon," said Amanda Phipps at the Fred Hutchinson Cancer Research Center in Seattle, who led the study.
Although it's not clear why that was the case, she said the finding could help researchers in the future target patients who are most likely to get a second cancer.
"The general message is very consistent now over several papers, that colorectal cancer patients have good outcomes, however even when cured they have an excess risk" of future cancers, said Dr. Jason Zell, who has also studied the topic at the University of California, Irvine.
He said there are a few possible explanations for the findings. First, treatment of colon cancer - whether with surgery, radiation or chemotherapy - could raise or lower the risk of cancer in nearby organs.
Another possibility is that more cancers are caught among people with a history of disease simply because they undergo more tests than the average patient.
Or, he told Reuters Health, "Maybe we've been underestimating the effects of common risk factors, like genetics... and also just diet and lifestyle."
Dr. Zell, who wasn't involved in the new research, said current studies are looking into whether second cancers can be prevented through exercise or healthier eating.
He said the findings shouldn't change treatment of colon cancer survivors, including how closely they are watched for other diseases. That's in part because there are no good screening tools for some of the cancers tied to colorectal cancer.
"For right now, I don't think it affects any screening recommendations directly," he said.
SOURCE: http://bit.ly/13lGETM
Cancer 2013.
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