Colon and Rectal Cancer
Colon and rectal cancers are alike in many ways, which is why we sometimes refer to them together as colorectal cancer. Symptoms and treatment can vary according to where the cancer grows, so it might be helpful for you to know more about the colon and rectum.
The colon and rectum are part of the digestive system (sometimes called the gastrointestinal or GI tract). The digestive system processes the food we eat and eliminates solid waste matter (feces or stool) from the body.
The digestive system consists of the esophagus, stomach, and the small and large intestines.
Where they grow
Colorectal cancers develop in the large intestine. The first 6 feet of the large intestine include the large bowel or colon. The final 6 inches make up the rectum and the anal canal. The anal canal ends at the anus (the opening of the large intestine to the outside of the body). The colon has 4 sections: the ascending colon, the transverse colon, the descending colon, and the sigmoid or S-shaped colon. Cancer can develop in any of the 4 sections of the colon or rectum.
How they grow
Colorectal cancers usually begin as a small clump of benign cells (called a polyp) that start to grow in the inner wall of the colon and rectum. Over time, some polyps can become cancerous. As the cancer grows, it can spread through the wall to nearby tissue outside the colon or rectum. Eventually, cancer cells may break away and spread to other parts of the body, where they form new tumors. This spreading process is called metastasis, and the new tumors are called metastases.
The diagnosis of colorectal cancer
The first step in the diagnosis of colorectal cancer may be a "digital rectal exam." In this test, which is often part of a routine physical exam, the doctor inserts a gloved finger into the rectum to feel for abnormal growths. If colorectal cancer is suspected, you and your doctor have many tests to choose from to make sure the diagnosis is correct. Since there is a wide range of options, knowing the differences can help you make a smart decision.
Before these tests (except the fecal occult blood test), your colon must be completely empty. To clean out your bowels before the procedure, you may be instructed to have an enema or drink a large volume of a liquid laxative prescribed by your doctor. This preparation is very important in ensuring the accuracy of the test.
Fecal occult blood test
In this simple, initial screening test for colorectal cancer, a stool sample is applied to a special card that turns color if any blood is detected.
A narrow tube is inserted into the rectum to allow liquid barium (a white, chalky liquid) into the colon. A special x-ray is then taken, in which tumors or masses appear as dark shadows. The barium makes it easier to see the tumors. Before this test, you will be told to fast (not eat or drink) for several hours.
A thin, lighted tube inserted into the rectum allows the doctor to look into the rectum and first section of the colon (where half of all polyps are found).
The most accurate and thorough test for colorectal cancer. A long, thin, lighted tube inserted into the rectum allows the doctor to look into the entire colon, remove polyps, and take tissue for biopsy. Polyp removal will prevent cancer from developing. A mild sedative is usually given with this test.
This noninvasive test uses images and sound waves to take a picture of the inside of the body. Unusual patterns in this image can indicate a mass or tumor. This test is used primarily to find cancer that has already spread to other organs.
Virtual colonoscopy (CT COLONOGRAPHY)
This test creates a 3-dimensional reconstruction of the colon to reveal any abnormal masses. Images are taken seconds after the colon is inflated with carbon dioxide through a small rectal tube. Virtual colonoscopy is a fairly new technology, so it is not yet clear how accurate it is.
Colon cancer is often well advanced when it is detected. That's why the American Cancer Society recommends some kind of screening test on a regular basis after the age of 50.
Stages of colorectal cancer
The stage of colorectal cancer, from stage 0 to stage IV, is one of the most important factors in selecting treatment options. Metastatic colorectal cancer is considered stage IV, which means that the cancer has spread to other organs in the body, such as the liver, lung, peritoneum (the wall of the abdomen and pelvis), or ovary. If you have any questions about your stage, ask the doctor, "Has the cancer spread to other parts of my body? If so, then where?"
Staging is a standardized process that tells the cancer care team how widespread the cancer may be. For all stages of colorectal cancer, surgery to remove the tumor (often called "segmental resection") is the primary treatment. Additional therapies may also be used.
Tumor is small in size and limited to the inside lining of the colon or rectum.
Tumor has moved into other layers of the colon, without spreading beyond the wall.
Tumor has gone through the wall of the colon or rectum, affecting nearby tissue, without affecting lymph nodes.
Tumor has spread to nearby lymph nodes, but not to other organs.
Tumor has spread to other organs and/or tissues such as liver and lungs.