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Potential Marker Found for Colorectal Cancer Blood Test

About 30% of colorectal tumors contain a form of gene silencing called loss of imprinting (LOI), which affects the growth promoting gene IGF2. A new study suggests that LOI may be a potential marker in a blood test for colorectal cancer risk.

Andrew P. Feinberg, M.D., of the Kimmel Cancer Center at Johns Hopkins University, and his colleagues analyzed blood and colonic mucosal samples from 172 patients who had undergone a colonoscopy for the presence of LOI in the IGF2 gene. They found that LOI was five times more likely to be present in individuals with a family history of colorectal cancer than in those without, and the odds of finding LOI in patients with a personal history of colorectal cancer was 22 times greater than in patients with no personal history of the disease. All patients with LOI in blood samples also had LOI in colonic mucosal samples. The researchers suggest that LOI may be used in a DNA-based blood test to predict an individual’s risk for colorectal cancer. The study appears in the March 14 issue of Science.

In an accompanying article, David F. Ransohoff, M.D., of the Lineberger Cancer Center at the University of North Carolina at Chapel Hill, noted that a noninvasive test that looks solely at the risk of colorectal cancer will only be clinically useful if a negative test strongly predicts a low lifetime risk of the disease, making conventional screening unnecessary. "Identification of a large subgroup of persons for whom conventional screening including colonoscopy is unnecessary would constitute a major advance in the development of cancer biomarkers," he wrote.

See also News, Vol. 94, No. 5, p. 332, "Stool Test Identifies Markers for Colorectal Cancer, Studies Show."

Daily Aspirin Reduces Risk of Colon Polyps

Taking an aspirin regularly—particularly the low-dose baby aspirin type—may reduce the risk of colon polyps in individuals at increased risk of colorectal cancer, according to results from two large randomized trials.

Laboratory tests in animals and observational studies in humans have suggested that regular aspirin use may decrease the risk of colon polyps, lesions that occasionally develop into cancer if untreated.

Robert S. Sandler, of the University of North Carolina, Chapel Hill, and his colleagues randomly assigned 635 patients who had a history of colorectal cancer to receive either 325 mg of aspirin (equivalent to a standard adult aspirin) or a placebo daily. After 31 months, 27% of patients in the placebo group had developed colon polyps, compared with 17% of patients in the aspirin group.

In a second study, John A. Baron, M.D., of the Dartmouth-Hitchcock Medical Center in Lebanon, N.H., and his colleagues randomly assigned 1,121 patients with a history of colon polyps to receive either a placebo, 81 mg of aspirin daily (equivalent to a baby aspirin), or 325 mg of aspirin daily. At three years, 47% of patients in the placebo group had developed new colon polyps, compared with 38% of patients in the baby aspirin group and 45% of patients in the adult aspirin group.

The two studies, published in the March 6 issue of the New England Journal of Medicine, indicate that aspirin can reduce the risk of colon polyps among patients at increased risk of colorectal cancer. "However, broad recommendations for the use of aspirin as a chemopreventive agent are premature and must be considered in the context of possible toxic effects as well as the potential benefits already provided by periodic surveillance colonoscopy," Baron and his colleagues wrote.

Report Focuses on Community Consequences of the Uninsured

A new report from the Institute of Medicine of the National Academies examines the strain that the uninsured population puts on the communities in which they live. In the United States, 41 million people lack health insurance.

The report, "A Shared Destiny: Community Effects of Uninsurance," found that communities with large uninsured populations are more likely to cut back on hospital services and divert tax dollars away from disease prevention and surveillance to compensate for medical care for the uninsured. In 2001, these diverted funds made up as much as 85% of the $34 billion to $38 billion in unreimbursed expenses incurred by the uninsured.

The report is the fourth in a series of reports by the IOM’s Committee on the Consequences of Uninsurance. The final report, due out in October, will suggest strategies for addressing the problem of uninsurance.

The full report is available from the Institute of Medicine at http://www.iom.edu.

    —Linda Wang



             
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