- The Colon
- The Rectum
- What Is Colon Cancer?
- What Is Rectal Cancer?
- Who Is at Risk for Colorectal Cancer?
- Signs and Symptoms of Colorectal Cancer
- Screening for Colorectal Cancer
- How Is Colorectal Cancer Diagnosed?
- Treatment for Colorectal Cancer
The digestive system is made up of the esophagus, stomach, and small and large intestines. The colon is the longest portion of the large intestine, measuring five to six feet in length. The first five feet consists of the colon; the remaining inches make up the rectum and the anus.
The colon’s function is to change liquid waste into solid stool. Stool can remain in the colon ten hours to several days before passing through the anus. The longer stool remains in the colon, the higher the risk of colon cancer.
The rectum, approximately five inches in length, is located to the end of the colon. The rectum normally is empty, except when stool is moved by the upper colon into the rectum prior to a bowel movement.
The anal canal attaches to the rectum and has strong internal and external valves called sphincters. These valves contract to retain the stool until it is time to have a bowel movement. The valves relax when releasing stool.
Colon cancer is the growth of abnormal tissue (or tumor) in the wall of the colon. Many tumors begin as normal tissue in the colon wall, then later change to adenomatous polyps or pre-cancerous growth. The polyp then grows larger and forms into a tumor. This growth can take many years, which increases the chance of early detection.
Rectal cancer is the growth of a tumor in the wall of the rectum. The tumor begins as normal tissue in the rectum wall, then later changes to adenomatous polyps that project from the rectal wall lining. The polyp then grows into a tumor. This growth also can take many years and increases the opportunity for early detection.
Colorectal cancer is the third most common cancer in the United States. African Americans have an increased risk of colorectal cancer. Other factors that put people at higher risk include:
- Age 50 and older (although numerous cases have been reported in younger people)
- Personal or family history of colon cancer, polyps or inherited colon cancer syndrome (i.e. FAP and HNPCC)
- History of ulcerative colitis or Crohn’s disease
- Diet high in fat and red meat
- Diet low in fruits and vegetables
- Diet high in calories
- Low level of physical activity
Even though studies show the factors mentioned above may increase the risk, about 80 percent of people diagnosed with colon cancer do not have a family history of the disease or present any high risk factors.
Signs and symptoms of colorectal cancer include:
- changes in bowel habits, such as diarrhea, constipation or narrowing (pencil-thin) of the stool, that last for an extended period of time
- rectal bleeding or blood in stool (stool appears bright red or very dark)
- feeling that the bowel does not empty completely
- frequent gas pains, bloating, cramps or fullness in the abdomen
- unexplained weight loss
- feeling weak and tired
- nausea or vomiting
The American Cancer Society recommends screening for colorectal cancer early detection as early as age 35 (depending on your level of risk). Screening options include:
- A fecal occult blood test (FOBT) or fecal immunochemical test (FIT) every year
- A flexible sigmoidoscopy every five years
- Annual FOBT (or FIT) and flexible sigmoidoscopy every five years
- A double-contrast barium enema every five years
- A colonoscopy every ten years
- Digital rectal examination (DRE) (specific to rectal cancer screening)
Click here to review additional screening guidelines from the American Cancer Society for people with high risk for colon cancer.
Abnormal polyps or tissue found in the rectum or colon is sent for a biopsy. Biopsy results will determine if the tissue is benign (non-cancerous) or malignant (cancerous). A "carcino-embryonic antigen" (CEA) blood test also is performed prior to treatment. CEA is a substance in the blood that increases when cancer is present.
If cancer is found, the chance of cure or recovery depends on:
- The stage of the cancer (whether the cancer is in the inner wall of the colon or rectum, involves the whole colon or rectum, or has spread to other organs in the body)
- The blood levels of CEA
- The patient’s general health
- Whether the cancer recurred
The National Comprehensive Cancer Network (NCCN) provides guidelines for the treatment of colorectal cancer.
The three most common forms of treatment are surgery, chemotherapy and radiation therapy.
The most common surgical treatments for colon cancer are:
- Local excision
- Resection of the colon (if the extent of the cancer makes it not possible to reconnect the colon, a colostomy (small opening in the abdominal wall) will be performed to allow the passage of stool)
- Radiofrequency ablation
- Abdominoperineal resection (APR) (performed for rectal cancer)
Chemotherapy may be recommended as a single agent or in combination with other drugs. The way chemotherapy is administered depends on the type and stage of cancer.
Chemoembolization of the hepatic artery may be used to stop the spread of cancer to the liver. This involves blocking the main artery that supplies blood to the liver by injecting chemotherapy between the blockage and the liver.
Radiation therapy is administered according to the type and stage of the cancer. It may be recommended prior to surgery, after surgery or in combination with chemotherapy.
Chemoradiation is recommended according to the type and stage of cancer.