Colon cancer is cancer that develops in the large intestine. The colon receives partially digested food from the small intestine. It helps to absorb water and additional nutrients. It is between the small intestine and rectum.
Symptoms of Colon Cancer
- Change in stool consistency (diarrhea or constipation)
- Bloody or dark stools
- Abdominal pain or cramps
- Anorexia and weight loss
Risk Factors of Colon Cancer
- Previous history of colorectal (colon or rectal) cancer or advanced polyps
- Family history of colorectal cancer
- Inflammatory bowel disease (such as Crohn’s disease or Ulcerative colitis)
- Diets high in fat and red meat and low in fiber, fruits and vegetables.
How Colon Cancer is Diagnosed
There are a variety of methods to diagnose colon cancer.
- Fecal occult blood tests – a stool sample is tested for trace amounts of blood that may not be visible. Although this may be due to an anal problem such as hemorrhoids, a positive test must always be followed by a full evaluation of the colon to search for the presence of cancer.
- Flexible Sigmoidoscopy – a shorter scope that is inserted through the anus to examine the rectum and lower one third of the colon. Suspicious lesions may be removed or sampled to check for cancer.
- Colonoscopy - a longer scope that may be used to view the entire rectum and colon. Suspicious lesions may similarly be removed or sampled to check for cancer. This is the most effective method for examining the entire colon.
- Double contrast barium enema – An x-ray test to examine the colon and rectum. Air and barium are inserted into the rectum and colon. A series of x-rays are obtained that may show abnormal masses. If this is positive, then a colonoscopy is usually performed to take samples for diagnosis. Although larger lesions are usually seen with a barium enema, many smaller lesions may be missed.
Adenomas, or pre-cancerous polyps, of the colon are a common condition. Most colon and rectal cancers develop from the lining of the colon, the mucosa, and go through a series of genetic changes. This is called the polyp-cancer sequence. Most cancers arise from adenomatous polyps. If polyps can be found and removed, your risk of cancer will be substantially reduced.
- Colonography (“virtual colonoscopy”) – a combination of a barium enema and CT scanning. A series of detailed x-rays are taken of the entire large intestine and then reconstructed on a computer. This is much more accurate that a simple barium enema, but small lesions may still be missed, and if the test is positive a colonoscopy must be performed to take samples for diagnosis.
Treatment Options for Colon Cancer at Tufts Medical Center
The type of treatment for colon cancer depends on the stage or extent of the cancer and its spread.
Colon cancer diagnosed at early stages, such as stage I and stage II cancer, is treated with surgical removal of the cancer and may not need further chemotherapy treatment.
More advanced stages of colon cancer may be treated with chemotherapy with or without surgery to eliminate colon cancer cells that may have spread elsewhere in the body. For some stage II and most stage III cancers it is recommended to remove the cancer by surgery and then treat with chemotherapy. The chemotherapy helps reduce the chance of the cancer returning.
For patients with metastatic, or stage IV colon cancer, chemotherapy is the mainstay of treatment. . Chemotherapy usually consists of one or more of the following agents: 5-fluorouracil, leucovorin, capecitabine, oxaliplatin and irinotecan. More recently biologic agents such as bevacizumab, cetuximab and panitumumab have been used in combination with chemotherapy or on their own. Surgery may be indicated for symptom relief, or for curative resection if the metastatic disease is stable and resectable.
In selected patients with a small number of liver or lung metastasis, localized treatment to these sites may be offered. When possible, surgical removal of the metastatic tumors is performed. In cases where surgery is not able to be done, highly focused radiation, called stereotactic body radiation, can be offered for treatment. In this treatment, higher doses of radiation are delivered over a few days (3-5) rather then over several weeks.
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