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INHERITED FORM OF COLON AND RECTUM CANCER MAY BE LESS COMMON THAN PREVIOUSLY REPORTED
Study Shows Much Lower Incidence for Most Common Inherited Colorectal Cancer
Irvine, Calif. -- INHERITED FORM OF COLON AND RECTUM CANCER MAY BE LESS COMMON THAN PREVIOUSLY REPORTEDThe largest study to date of a form of inherited colorectal cancer known as hereditary nonpolyposis colorectal cancer (or HNPCC) shows that this form of the disease may be far less common than previous studies have reported, according to scientists at UC Irvine's College of Medicine.
The study indicates that far fewer people with family histories of colorectal cancer actually are at risk from getting the HNPCC form of the disease. However, the researchers warn that people with family histories of colorectal cancer may be susceptible to other genes that are unknown and could cause the disease.
HNPCC is the most common of genetic colorectal cancers and is marked by the sudden growth of cancerous tumors without the pre-cancerous polyps, or growths, seen in other colorectal cancer patients.
David Peel, assistant professor, and Hoda Anton-Culver, professor of epidemiology at UCI, and colleagues studied 1,134 patients with colorectal cancer living in Southern California. They found that about 1 percent of them had HNPCC. Previous studies reported rates of around 5 percent and a few studies reported rates up to 13 percent. The UCI study appears in the Sept. 20 issue of the Journal of the National Cancer Institute.
"Studies have shown that family history is a strong factor in determining the risk of getting colorectal cancer, so it is very important to determine the exact rates of its inherited forms," Anton-Culver said. "This study helps us pin down the risks of inheriting the disease and indicates that researchers still need to look for other genetic interactions that may lead to colorectal cancer. While we've shown that HNPCC is not as common as we thought, other unknown genes could be contributing to the risk of getting colorectal cancer."
Of the 1,134 patients in the study, 227 had a family member who had colorectal cancer and 16 patients had HNPCC. None of the patients older than 65 years in the study had this hereditary form of the disease, indicating that HNPCC tends to strike younger people. Of patients under 65, the incidence of HNPCC was 2.1 percent, resulting in an overall average of about 1 percent.
The researchers also found that endometrial cancer and cancer of the ureter (which drains urine from the kidney to the bladder) were moderately more prevalent in families of patients with HNPCC, which may indicate a genetic susceptibility to other cancers. In addition, the study bolstered evidence of a link between this inherited form of the disease and mutations in genes called MSH2 and MLH1, which have previously been associated with HNPCC.
Colorectal cancer is the most common cancer affecting the digestive system; about 130,000 new cases are diagnosed every year. It is one of the three leading causes of cancer deaths in the United States. The overall risk of developing this cancer in a person's lifetime is estimated at about 6 percent nationally. About 80 percent of colorectal cancers do not run in families.
"HNPCC is less common than previously assumed, but there are probably many other kinds of inherited colon cancer," Peel said. "If somebody has a mutation in the appropriate gene, he or she is more likely to get colorectal cancer; we need to continue searching for other genes that may play a role in this disease."
Peel and Anton-Culver's colleagues in this study included Agryrios Ziogas, Maureen Gildea, Beth Laham and Enedina Clements at UCI; Edward A. Fox at Dana-Farber Cancer Institute, Boston, Mass., and Richard Kolodner at UC San Diego.
The research, supported by the National Cancer Institute and the Lon V. Smith Foundation, is part of the UCI-UCSD Cancer Genetics Network Center, which was established through a grant from NCI to study the complex genetic interactions in cancer. Under the direction of Anton-Culver, the center at UCI is one of eight research institutions nationwide that make up the Cancer Genetics Network, which was established in 1998 by NCI.
Much of the research is taking place at the UCI Biomedical Research Center, which is providing much-needed laboratory and clinical facilities for researchers addressing the major health challenges of the 21st century. When complete, the center will focus on research in the neurosciences, the genetics of cancer, immunology and infection and other medical issues. The center's first building, the Gillespie Neuroscience Research Facility, is home to the Reeve-Irvine Research Center and Institute for Brain Aging and Dementia. Construction of the second building, the Robert R. Sprague Family Foundation Hall, began in February.
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Contact:Andrew Porterfield(949) 824-3969[email protected]
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