Colorectal cancer refers to cancer that starts in the colon and the rectum, which constitute the last parts of the digestive system. Specifically, they form the large intestine, the colon covering about the first 5 feet (1.52 meters) of the organ and the rectum comprising around the last 5 inches (12 centimeters). The United Nations considers colorectal cancer the world's third most frequently diagnosed malignancy, with inhabitants of developed countries being the worst afflicted. Although no one knows the exact causes of colorectal cancer, there are several risk factors that doctors list as contributing to the occurrence of this common form of cancer.
The most common risk factors for colorectal cancer appear to be age and genetics. According to the National Cancer Institute (NCI), more than 90 percent of all cases concern patients over the age of 50. A person with a history of colorectal cancer, particularly early in life, is more likely to develop it again in the future. If a close relative, especially a sibling or parent, has or has had it, the risk further increases. Lynch Syndrome in particular, which is also known as hereditary nonpolyposis colon cancer (HNPCC), could be one of the causes of colorectal cancer, representing the most common form of genetic colorectal cancer and approximately 2 percent of cases concerning this disease.
Other major factors that may be considered as causes of colorectal cancer include smoking and diet. A 2000 report by the American Cancer Society (ASC) stated that female smokers were 40 percent more likely to die of the disease than women who did not smoke, and male smokers were 30 percent more likely than male non-smokers. The European Prospective Investigation into Cancer and Nutrition (EPIC) conducted a study in 2005 that theorizes that people who have diets high in fat and red meat but low in fiber, fruit and vegetables have an increased risk of developing colorectal cancer.
Several other factors exist as possible causes of colorectal cancer. These include significant alcohol intake, inflammatory bowel diseases such as ulcerative colitis or Crohn's disease, lack of exercise and viruses. Even though more work needs to be done to truly determine the causes of colorectal cancer, people can take certain measures in an effort to avoid it. Those who have family histories of this particular cancer are strongly encouraged to have frequent medical check-ups, and a healthier diet and exercise may help in preventing the disease.