About Colon Cancer
Colon cancer often begins as small polyps, or adenomatous cells, in the large intestine. The large intestine, also called the colon, is the last part of the digestive tract, and follows the small intestine. Most polyps are benign or premalignant, but if undetected, some can become cancerous over time. Colon cancer can often be prevented, through regular screening tests, such as a colonoscopy.
Although colon cancer rarely shows any symptoms during its early stages, there are warning signs:
• change in bowel habits
• blood in the stool
• recurring stomach discomfort such as gas, cramping, or pain
• weakness or fatigue
• unexplained weight loss
Factors that may increase the risk of colon cancer:
• inflammatory bowel disease such as ulcerative colitis or Crohn's disease
• high-fat, low-fiber diet
• sedentary lifestyle
• family history of colorectal cancer or colon polyps
The risk of colon cancer also increases with age; 90 percent of patients who develop colon cancer are age 50 or older.
Screening and Diagnosis
Combined with regular screening and proper treatment of polyps and cancers in the earliest stages, colon cancer can be cured almost 100 percent of the time. A colonoscopy is considered to be the best screening and diagnostic test for colon cancer.
A colonoscopy uses a colonoscope to visually examine the colon and rectum for polyps and tumors. A colonoscope is a thin, flexible tube, with a tiny fiber-optic video camera and a light inside its tip. It is about the thickness of an adult finger. The tube is flexible and can be maneuvered to investigate the interior surface of the colon. The camera sends magnified images of the colon to a television screen.
The colonoscope can be used to perform treatment as well as viewing the colon. Small surgical instruments, inserted through the colonoscope, can be used to remove small polyps that are discovered during the examination, without having to perform major surgery.
To prepare for a colonoscopy, a patient is usually required to drink a liquid or perform bowel cleansing using laxatives and sometimes enemas. This eliminates all fecal matter (stool) from the colon so that the person conducting the test will have a clear view.
Virtual Colonoscopy (CT colonography)
Virtual Colonoscopy, also called CT Colonography, is a minimally invasive alternative to colonoscopy, producing 2D and 3D images of the colon that are displayed on a screen. It uses a CT scanner to produce hundreds of cross-sectional images that provide a detailed view of the colon's interior, from the lower end of the small intestine to the rectum, without needing to insert a colonoscope. This procedure is suited for patients who are frail, older, or for other reasons aren't able to undergo a colonoscopy. Properly performed, a virtual colonoscopy is as accurate in detecting polyps as a traditional colonoscopy. If polyps are found during the exam, a colonoscopy can be performed to remove the polyp.
A sigmoidoscopy is similar to a colonoscopy in that it uses a flexible tube with a fiber-optic camera and light, but examines only the last two feet of the intestine, called the sigmoid colon, and rectum.
DNA Stool Test
The DNA Stool Test is a noninvasive test to detect polyps and early-stage cancers in the colon. After the patient's stool is mailed to the lab, the stool is analyzed for genetic mutations in the DNA that signal the existence of polyps and cancers. Although not as common as a colonoscopy, the DNA Stool Test is a noninvasive alternative that doesn't require bowel cleansing, patient sedation or a trip to the clinic. In addition to detecting colon cancer, future applications of the DNA Stool Test include detecting malignancies through the digestive tract, the throat, esophagus, stomach, pancreas, bile ducts and small bowel.
Colon cancer staging tests estimate how far a particular cancer has penetrated into the colon, whether the cancer has spread to nearby lymph nodes or organs, and to determine the best method of treatment. Most colon cancer staging tests are done after surgery has been performed and pathology reports have been reviewed. Before undergoing additional surgery or other treatments, a patient will likely have an abdominal CT scan and a lung X-ray to determine whether cancer has spread to these other areas.
The most common staging system is called the TNM System (tumors/nodes/metastases). The "T" is for the degree of invasion of the intestinal wall, "N" for degree of lymphatic node involvement, and "M" for the degree of metastasis.