CRC is a common and lethal disease. In the United States, CRC is the third most commonly diagnosed cancer and the second leading cause of cancer death. Approximately 148,610 new cases of CRC are diagnosed each year in the United States, of which 106,680 are colon and the remainder rectal cancers. Globally, the incidence of CRC varies ten-fold, with the highest incidence rates in North America, Australia and northern and western Europe.
Environmental and genetic factors can increase the likelihood of developing CRC. Consider the following, all of which elevate an individual's risk of developing CRC:
Screenings can detect CRC when it can be treated. In the meantime, certain practices have been identified as protecting the body against CRC, including:
Symptoms vary depending on the location of the cancer within the colon or rectum, though there may be no symptoms at all. The most common presenting symptom is rectal bleeding. Cancers arising from the left side of the colon generally cause bleeding, and in their late stages may cause constipation, abdominal pain and obstructive symptoms. On the other hand, right-sided colon cancer may produce vague abdominal aching or weakness, weight loss and anemia from chronic blood loss.
Men tend to get colorectal cancer at an earlier age than women, but women live longer so they 'catch up' with men and, thus, the total number of cases in men and women is equal. In the United States, incidence rates of colon cancer declined by 3 percent between 1998 and 2000. During the period from 1996 to 2000, the average annual incidence rates per 100,000 population were 64.2 from men and 46.7 for women. Despite such data, during the same time period, the incidence rates for right-sided cancer increased, particularly in women. In addition, while tobacco and alcohol increase the risk of colorectal cancer, women who smoke are a higher risk. Among women, CRC screening rates are still relatively low (30-40%) and are comparable to mammography rates 20 years ago. African Americans are at a much higher risk for colon cancer than other races. They have a significantly lower age at diagnosis and experience a larger number of polyps and cancer in the proximal colon. Their survival is reduced compared to Caucasians.
Age is a major risk factor for sporadic CRC. The lifetime incidence of CRC in patients at average risk is about 5 percent, with 90 percent of cases occurring after the age of 50.
Most colon and rectal cancers originate from benign wart-like growths on the inner lining of the colon or rectum called polyps. Not all polyps have the potential to transform into cancer. Those that do are called adenomas. It takes more than 10 years in most cases for an adenoma to develop into cancer. Screening identifies cancers earlier, before symptoms develop, which dramatically improves the chance of survival. Identifying and removing polyps before they become cancerous actually prevents the development of colorectal cancer. The pathologic stage at diagnosis remains the best indicator of long-term prognosis. The most important characteristics are the presence of distant metastases, local tumor extent, nodal positivity and residual disease. Five-year survival rates vary from 93 percent for stage I to 8 percent for stage IV colon cancer. Five-year survival rates for rectal cancer tend to be somewhat lower.
The American College of Gastroenterology considers colonoscopy the preferred screening test, but the following tests are available:
Screenings can detect CRC when it can be treated. For individuals at normal risk, screening tests should begin at age 50. The preferred approach is a screening colonoscopy conducted every 10 years. In addition, consider the following recommendations for screening:
Screening colonoscopy is done under conscious sedation using a combination of painkiller and sedative given intravenously. Patients are usually comfortable during and after the colonoscopy. The day before the procedure, the patients need to take a bowel preparation, which is available in different forms and well tolerated. Complications including perforation and major bleeding are unusual, about one to two per 1,000 procedures.
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