Colon cancer occurs when the cells in the colon or rectum grow and multiply uncontrollably, damaging surrounding tissue and interfering with the normal function of the colon or rectum. Colon cancer is the third most common cancer diagnosed in the United States. Most colon cancers (about 70 percent) are found in the first six feet of the large intestine. The other 30 percent occur in the last 10 inches of the large intestine (rectum). Collectively they are referred to as colorectal cancers.
One in 19 Americans will be diagnosed with colon cancer in their lifetime, for an overall risk of 5.4 percent. Although colon cancer affects men and women equally, rectal cancer is more common in men. When colon and rectal cancers are found early, there is nearly a 90 percent chance for cure. About 80 percent of colon cancer cases are sporadic, meaning that cause is nonspecific or undetermined. The other 20 percent of colon cancers are hereditary. People who have a first-degree family member with colon cancer are more likely to be affected themselves. About 5 percent of this group has a predisposition to hereditary non-polyposis colorectal cancer (Lynch syndrome), a rare disease that generally strikes people aged 30 to 50.
There often are no symptoms of colon cancer in its early stages. Most colon cancers begin as a polyp, a small non-cancerous growth on the colon wall that can grow larger and become cancerous. As polyps grow, they can bleed or obstruct the intestine.
- Rectal bleeding
- Blood in the stool or toilet after a bowel movement
- Prolonged diarrhea
- A change in size or shape of your stool
- Abdominal pain or a cramping pain in your lower stomach
- A feeling of discomfort or urge to have a bowel movement when there is no need
Many colon symptoms are not cancer, but if you notice one or more of these symptoms for more than two weeks, see your doctor.
There are many methods for diagnosing colon cancer. Some of these procedures are also used as screening devices to detect colon cancers in the early stages, when treatment is more successful.
Fecal Occult Blood Test (FOBT): A stool sample is examined for traces of blood not visible to the naked eye. If you do see blood in your stool, contact your doctor immediately.
Fecal Immunochemical Test (FIT): FIT is a take-home test that detects blood proteins in stool. A small, long-handled brush is used to collect a stool sample, which is placed on a test card and sent to a lab for examination.
Sigmoidoscopy: A tiny camera with flexible plastic tubing is inserted into the rectum, providing a view of the rectum and lower colon. This procedure can also be used to remove suspicious tissue for examination.
Colonoscopy: A colonoscope is a longer version of a sigmoidoscope, and can examine the entire colon. Patients must be sedated for a colonoscopy.
Double Contrast Barium Enema (DCBE): Barium is a chemical that allows the bowel lining to show up on X-ray. A barium solution is administered by enema; then the patient undergoes a series of X-rays.
Digital Rectal Exam: The doctor inserts a gloved finger into the rectum to feel for polyps or other irregularities.
Carcinoembryonic Antigen (CEA): A blood test that determines the presence of CEA, a substance, or tumor marker, produced by some cancerous tumors. This test can also be used to measure tumor growth or assess if cancer has recurred after treatment.
Stage 0: The cancer is found only in the innermost lining of the colon or rectum. Carcinoma in situ is another name for Stage 0 colorectal cancer.
Stage I: The tumor has grown into the inner wall of the colon or rectum. The tumor has not grown through the wall.
Stage II: The tumor extends more deeply into or through the wall of the colon or rectum. It may have invaded nearby tissue, but cancer cells have not spread to the lymph nodes.
Stage IIA: Cancer has spread beyond the middle tissue layers of the colon or rectum wall or has spread to nearby tissues around the colon or rectum
Stage IIB: Cancer has spread beyond the colon or rectum wall into nearby organs and/or through the peritoneum
Stage III: The cancer has spread to nearby lymph nodes, but not to other part of the body.
Stage IV: The cancer has spread to other parts of the body, such as the liver or lungs.
Surgery is the most common treatment for colon and rectal cancers. Depending on the stage and location of the tumor, different surgical methods are used.
Local excision: If tumors are small enough, they may be removed with minimally invasive surgery. Tiny incisions are made in the abdomen. A miniature camera and surgical instruments are inserted. The surgeon uses computer imaging to locate and remove the tumor.
Polypectomy: Suspicious or cancerous polyps on the colon wall can easily be removed. A colonoscope is a long tube with a camera in the end. The colonoscope is inserted in the rectum and guided to the area requiring treatment, and a tiny, scissor-like instrument removes the polyp.
Colectomy: Surgeons remove the cancerous portion of the colon, along with a margin of healthy tissue on either side, and then join the colon back together.
This procedure is also called a hemicolectomy or segmental resection.
Resection & colostomy: If the colon cannot be rejoined after removing the cancer, surgeons will perform a colostomy. A stoma (hole) is cut in the abdominal wall and attached to a segment of colon. Bodily waste goes through the stoma into a plastic bag outside the body. Colostomies may be temporary, allowing the bowel to heal before resection. However, about 15 percent of colostomies are permanent.
Radiation therapy may be used to destroy any colon or rectal cancer cells that remain after surgery. Radiation is used most often on locally advanced rectal cancers prior to surgery along with chemotherapy, or those that cannot be treated with surgery. It can also be used to relieve cancer symptoms.
Chemotherapy can be used to shrink rectal tumors before surgery, or to lengthen survival time after surgery. Chemotherapy is generally not effective for advanced or recurring colon cancers.
Researchers are developing new drugs that are designed to seek out and destroy specific types of cancer cells without affecting healthy cells.
New treatments are always being tested in clinical trials and some patients with cancer may want to consider participating in one of these research studies. These studies are meant to help improve current cancer treatments or obtain information on new treatments. Talk to your doctor about the clinical trials that may be right for you.