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Colorectal cancer (also known as colon cancer, rectal cancer, or bowel cancer) is the development of cancer in the colon or rectum (parts of the large intestine). It is due to the abnormal growth of cells that have the ability to invade or spread to other parts of the body.〔(【引用サイトリンク】url=http://www.cancer.gov/cancertopics/cancerlibrary/what-is-cancer )〕 Signs and symptoms may include blood in the stool, a change in bowel movements, weight loss, and feeling tired all the time. Risk factors for colorectal cancer include lifestyle, older age, and inherited genetic disorders.〔 Other risk factors include diet, smoking, alcohol, lack of physical activity, family history of colon cancer and colon polyps, presence of colon polyps, race, exposure to radiation, and even other diseases such as diabetes and obesity.〔 Genetic disorders only occur in a small fraction of the population. A diet high in red, processed meat, while low in fiber increases the risk of colorectal cancer.〔 Other diseases such as inflammatory bowel disease, which includes Crohn's disease and ulcerative colitis, can increase the risk of colorectal cancer.〔 Some of the inherited genetic disorders that can cause colorectal cancer include familial adenomatous polyposis and hereditary non-polyposis colon cancer; however, these represent less than 5% of cases.〔〔 It typically starts as a benign tumor, often in the form of a polyp, which over time becomes cancerous.〔 Bowel cancer may be diagnosed by obtaining a sample of the colon during a sigmoidoscopy or colonoscopy.〔 This is then followed by medical imaging to determine if the disease has spread.〔 Screening is effective for preventing and decreasing deaths from colorectal cancer.〔 Screening is recommended starting from the age of 50 to 75. During colonoscopy, small polyps may be removed if found. If a large polyp or tumor is found, a biopsy may be performed to check if it is cancerous. Aspirin and other non-steroidal anti-inflammatory drugs decrease the risk.〔 Their general use is not recommended for this purpose, however, due to side effects. Treatments used for colorectal cancer may include some combination of surgery, radiation therapy, chemotherapy and targeted therapy.〔 Cancers that are confined within the wall of the colon may be curable with surgery while cancer that has spread widely are usually not curable, with management focusing on improving quality of life and symptoms.〔 Five year survival rates in the United States are around 65%.〔(【引用サイトリンク】url=http://seer.cancer.gov/statfacts/html/colorect.html )〕 This, however, depends on how advanced the cancer is, whether or not all the cancer can be removed with surgery, and the person's overall health.〔 Globally, colorectal cancer is the third most common type of cancer making up about 10% of all cases. In 2012 there were 1.4 million new cases and 694,000 deaths from the disease.〔 It is more common in developed countries, where more than 65% of cases are found.〔 It is less common in women than men.〔 ==Signs and symptoms== The signs and symptoms of colorectal cancer depend on the location of the tumor in the bowel, and whether it has spread elsewhere in the body (metastasis). The classic warning signs include: worsening constipation, blood in the stool, decrease in stool caliber (thickness), loss of appetite, loss of weight, and nausea or vomiting in someone over 50 years old. While rectal bleeding or anemia are high-risk features in those over the age of 50, other commonly-described symptoms including weight loss and change in bowel habit are typically only concerning if associated with bleeding.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Colorectal cancer」の詳細全文を読む スポンサード リンク
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