This new tool may assist health care providers and their patients in making informed choices about when and how to screen for colorectal cancer and can be used in designing colorectal cancer screening and prevention trials. An article describing the new risk-assessment model and a second article describing its validation appear online December 29, 2008, in the Journal of Clinical Oncology. The risk assessment tool is available on the NCI Web site at wwwncer/colorectalcancerrisk, and people using this tool should work with their health care providers to interpret the results.

Using easily obtainable information (e.g., personal and family medical history, lifestyle behaviors, and age), the tool provides an estimate of an individual's risk of developing colorectal cancer over certain time periods (within five years, 10 years, and over the course of a lifetime). This risk-assessment model is the first to provide an absolute risk estimate for colorectal cancer (i.e., the probability of developing colorectal cancer over a given period of time) for the general, non-Hispanic white population age 50 or older in the United States.

"Much like the NCI's breast cancer and melanoma risk assessment tools, this new colorectal cancer risk assessment tool should prove useful not only in counseling patients on their individual risk, but also in helping plan the type and frequency of screening interventions," said NCI Director John E. Niederhuber, M.D. "As we move toward an era of personalized medicine, the ability to assess an individual patient's cancer risk and thereby improve our ability to apply appropriate prevention measures is of vital importance."

Approximately one in 18 Americans will develop colorectal cancer at some point during his or her lifetime. In 2008, an estimated 148,810 people will be diagnosed with colorectal cancer in the United States and another 49,960 will die of the disease. There are several screening options for colorectal cancer, including fecal occult blood tests (which look for the presence of blood in stool samples), sigmoidoscopy (which uses a lighted probe to inspect the sigmoid, or lowest part, of the colon), colonoscopy (which uses a lighted probe to inspect the entire colon), and computerized tomographic colonography, also known as virtual colonoscopy (which uses CT scans, a type of x-ray, to create images of the entire colon). Having additional information about an individual's risk could aid health care providers and their patients in making decisions about which screening regimen to pursue.

To develop the risk-assessment model, researchers used data from two large population-based case-control studies. Several factors that have been previously associated with colorectal cancer risk were shown to be predictive of a colorectal cancer diagnosis in those two studies, including age; family history of colorectal cancer; consumption of vegetables; body mass index; cigarette smoking; use of aspirin or other non-steroidal anti-inflammatory drugs; physical activity; use of hormone replacement therapy; previous history of sigmoidoscopy and/or colonoscopy; and history of polyps. Estimates of relative risk (comparisons of risk in one group to another) from the case-control studies were combined with population-based data on colorectal cancer incidence from NCI's SEER (Surveillance, Epidemiology and End Results) cancer registries to make the model broadly applicable in the United States.

"This colorectal cancer risk model should provide physicians and their patients a new tool to help make informed decisions about cancer screening and other cancer prevention strategies. It may also assist policy makers in evaluating the usefulness of current and future population colorectal cancer screening approaches," said Andrew Freedman, Ph.D., lead author of the paper that describes the development of the risk-assessment model.

To test the accuracy of the risk-assessment model, the researchers compared expected numbers of colorectal cancer cases predicted by the model to the observed numbers of cases identified in the NIH-AARP Diet and Health Study, a large study that follows AARP members and collects information about nutrition and health. From information about individual risk factors that was collected when participants entered the study, the researchers used the new model to estimate the number of men and women who would be expected to develop colorectal cancer. According to Ruth Pfeiffer, Ph.D., who was the senior author of the validation study, "The colorectal cancer risk-assessment tool predicted the numbers of colorectal cancer diagnoses well overall, and in most risk categories."

Because the majority of participants in the two case-control studies used to develop the model were non-Hispanic whites age 50 or older, the researchers were unable to estimate relative risks for other age and racial/ethnic groups. However, there are plans to expand the tool to include these populations in the future. In addition, the tool is not applicable to individuals with certain gastrointestinal disorders (such as ulcerative colitis or Crohn's disease), certain inherited genetic conditions (such as familial adenomatous polyposis or hereditary nonpolyposis colorectal cancer) or a personal history of colorectal cancer. These conditions are known to carry a very high risk of developing colorectal cancer.

In addition to the standard Web tool, a mobile Web-based version for use on Internet-enabled mobile devices and the source code for the model will soon be made available to researchers. It is important that users of the online tool work with their primary health care provider to interpret the results and plan a course of action regarding colorectal cancer screening.

To view the new Colorectal Cancer Risk Tool online, please visit: wwwncer/colorectalcancerrisk.

For more information about understanding cancer risk, please visit: understandingriskncer.

NCI leads the National Cancer Program and the NIH effort to dramatically reduce the burden of cancer and improve the lives of cancer patients and their families, through research into prevention and cancer biology, the development of new interventions, and the training and mentoring of new researchers. For more information about cancer, please visit the NCI Web site at cancer or call NCI's Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).

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