Colon cancer is cancer of the large intestine (colon), the lower part of the digestive system. Rectal cancer is cancer of the last several inches of the colon. Together, they're often referred to as colorectal cancer.
Symptoms of colorectal cancer are numerous and nonspecific. They include
- Fatigue and weakness
- Change in bowel habits (such as diarrhea, constipation, and narrowing of the stool) that lasts for more than a few days
- Red or dark blood in stool
- Abdominal pain
- Cramps or bloating.
Many people with colon cancer experience no symptoms in the early stages of the disease. When symptoms appear, they'll likely vary, depending on the cancer's size and location in the large intestine.
Screening and Diagnosis
Colorectal cancer screening and diagnosis may involve one or more of a number of procedures:
- Colonoscopy : This examination allows the doctor to inspect the rectum and colon, using a thin tube that has a light on the end. It is inserted into the rectum while the patient lies on his or her side. Patients often receive a mild sedative during this procedure to ensure their comfort. Any polyps or other growths that are found during these examinations are usually removed at the time and sent to a laboratory for examination.
- Fecal Occult Blood Test : Also known as a stool blood test, this laboratory test looks for blood in the stool. The patient is asked to follow a special diet and then bring in stool specimens (usually applied to small, folded cards) from three successive days.
- Flexible Sigmoidoscopy : This examination is similar to the colonoscopy exam, but it uses a shorter tube to inspect the lower colon.
Virtual colonoscopy is a technique that uses CT scans to create a 3-D image that can be used to evaluate the bowel. At this time, it is still a research tool and is not generally available. It is also important to note that, while this is a promising technique, it does not allow for a biopsy or polyp removal at the same time an abnormality is found.
Staging of colon cancer
Once a person has been diagnosed with colon cancer, the doctor orders for tests to determine the extent (stage) of the cancer. Staging helps determine what treatments are most appropriate for an affected person.
- Staging tests may include imaging procedures such as computed tomography (CT) and magnetic resonance imaging (MRI) scans, which may be used to see if the cancer has spread to other organs, such as the liver and lungs.
- chest x-ray, which may be performed to see if the cancer has spread to the lungs
- blood tests for CEA, a protein that acts as a marker for colorectal cancer.
The stages of colon cancer are:
- Stage I: The cancer has grown through the superficial lining (mucosa) of the colon or rectum but hasn't spread beyond the colon wall or rectum.
- Stage II: The cancer has grown into or through the wall of the colon or rectum but hasn't spread to nearby lymph nodes.
- Stage III: The cancer has invaded nearby lymph nodes but isn't affecting other parts of the body yet.
- Stage IV : The cancer has spread to distant sites, such as other organs — for instance to the liver or lung.
The type of treatment a doctor recommends will depend largely on the stage of the cancer. Treatment options include surgery, radiation therapy, chemotherapy, and combinations of these approaches.
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