Early detection and prevention of colorectal cancer (review)

Colorectal cancer is a leading cause of cancer-related deaths, and the two most important considerations for avoidance of this disease are early detec tion and prevention. If metastasis has occurred to distant sites, such as t he liver and lung, the 5-year survival rate for colorectal cancer is below 10%, but this increases to greater than 90% when the cancer is found early. Early detection can be facilitated by use of the digital rectal exam, feca l occult blood test, sigmoidoscopy, and colonoscopy, but these methods migh t be supplemented in the future by other screening assays using intermediat e biomarkers. One interesting biomarker, the aberrant crypt focus (ACF), ha s been observed in resected human colons, and is the earliest detectable mo rphological change in the colons of experimental animals treated with carci nogens such as the cooked meat heterocyclic amines. The ACF can also be use d as an end-point to screen for potential inhibitors of colorectal cancer; using this approach, we identified conjugated linoleic acids, indole-3-carb inol, chlorophyllin, and tea polyphenols as promising inhibitors in the col on. These compounds can be added to a growing list of natural and synthetic agents that might be effective against colorectal cancer, including seleni um, calcium, and nonsteroidal anti-inflammatory agents. However, results fr om human clinical trials with several of these compounds have highlighted t he need for detailed mechanism data before recommendations can be made for wide-scale use in humans. In the meantime, the best approach to reducing th e risk of colorectal cancer would be to increase the dietary intake of frui ts, vegetables and cereals, while reducing the overall intake of fat, parti cularly from animal sources.