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特集：医療英語 > 第 29 回：Colorectal Cancer (結腸直腸癌)
In 2005, approximately 115,000 new patients were diagnosed with colorectal cancer in Japan, making it one of the most common types of cancer in the country1. In the past fifty years the incidence of colorectal cancer in Japan has increased significantly2. Colorectal cancer includes both colon cancer (cancer of the large intestine, the lower part of the digestive system) and rectal cancer (the last six inches of the colon).
Colorectal cancer often begins as adenomatous polyps, which are small, benign (noncancerous) clumps of cells. They are usually mushroom-shaped, but may also be flat or recessed into the colon wall (nonpolypoid lesions). Over time, some of the polyps may become cancerous. In the early stages, many patients do not experience any symptoms. As the cancer progresses, some of the symptoms may include rectal bleeding or blood in the stool, persistent cramping, gas and abdominal pain. Symptoms vary depending on the cancer\'s size and location.
If symptoms are present, a colonoscopy is usually performed. Preparation for a colonoscopy involves taking a laxative and drinking a large amount of fluid to clean out the colon. Then a colonoscope, a long, slender, flexible tube attached to a video camera and monitor, is used to view the colon. If polyps are found during the exam, the doctor usually removes them or takes a tissue sample for laboratory analysis.
If cancer is diagnosed, it is then staged to determine the appropriate course of treatment:
- Stage 0 - Earliest stage. Cancer is present in the colon or rectum mucosa (inner layer) only. Also called carcinoma in situ.
- Stage I - Cancer has grown through the mucosa but has not spread beyond the colon wall or rectum.
- Stage II - Cancer has grown through the colon or rectum wall but has not spread to lymph nodes nearby.
- Stage III - Cancer has spread to nearby lymph nodes but isn\'t affecting other parts of the body.
- Stage IV - Cancer has metastasized to other parts of the body. Recurrent ? Cancer has returned after treatment. It may recur in the colon, rectum or another part of the body.
The primary treatments for colorectal cancer can be used alone or in combination:
- Surgery - The cancerous portion of the colon or rectum is removed, and the healthy portions are reconnected if possible. Otherwise, a colostomy is required. An opening in the abdomen wall is created from a portion of the remaining bowel for the elimination of body waste into a special bag. Side effects of surgery may include temporary pain, constipation and diarrhea.
- Chemotherapy - Drugs are used to destroy cancer cells. Chemotherapy is often used in combination with surgery, radiation therapy, and/or targeted colorectal cancer drugs. Possible side effects may include nausea, vomiting, mouth sores, fatigue, hair loss and diarrhea.
- Radiation therapy - X-rays or another powerful energy source are used to kill cancer cells. It is often used in combination with other treatments. Side effects may include diarrhea, rectal bleeding, fatigue, loss of appetite, and nausea.
- Targeted drug therapy - Drugs that specifically target the cancer cells include bevacizumab (Avastin), which prevents tumors from developing new blood vessels, as well as cetuximab (Erbitux) and panitumumab (Vectibix), which target a chemical signal that instructs cells to divide an reproduce. Not all of these drugs have been approved in all countries, so they may still be considered experimental in some parts of the world.
To prevent colorectal cancer, screening should begin at age 50. Screening should begin sooner for people at increased risk. The primary risk factors for colorectal cancer include age (90% of people diagnosed are older than fifty), history of adenomatous polyps, inflammatory intestinal conditions such as ulcerative colitis, inherited disorders that affect the colon, family history of colon cancer and polyps, diet (the risk of colon cancer increases when people move from a developing country to a Western country and adapt to the Western diet), sedentary lifestyle, diabetes, obesity, smoking, alcohol, growth hormone disorder, and radiation therapy for cancer directed at the abdomen3.
- Steps that can be taken to prevent colorectal cancer include:
- Eat a diet rich in fruits, vegetables and whole grains, as well as a variety of foods to increase the consumption of vitamins and minerals
- Limit fat, especially saturated fat
- Limit alcohol consumption
- Refrain from smoking
- Be physically active
- Maintain a healthy body weight
- Please summarize the article. What is the main point of the article?
- What is colorectal cancer?
- What is the incidence of colorectal cancer and what has been the trend over the past fifty years?
- What are the symptoms of colorectal cancer?
- Why is colorectal cancer staged? What are the stages?
- How is colorectal cancer treated?
- What are the risk factors for colorectal cancer?
- How can colorectal cancer be prevented?
- Oshima A, Kuroishi T, Tajima K. "Cancer White Paper - Incidence/Death/Prognosis - 2004" Shinoharashinsha Inc.
- Koyame Y, Kotake K. Overview of colorectal cancer in Japan: report from the Registry of the Japanese Society for Cancer of the Colon and Rectum.; Dis Colon Rectum 1997, Oct, 40 (10 Suppl): S2-9.
- Colon Cancer. Mayoclinic.com. Accessed 19 March 2008.