The Colon

The colon and the rectum make up the large intestine, the final segment of the digestive system. The colon is a tubular muscle, lined with a layer of mucous cells that help the chyme (food combined with the body’s digestive fluids) continue its journey through the bowel and out of the anus by lubricating the path. Glands resembling skin pores extract any water remaining in the food residue. The colon then moves rest of the waste material to the rectum in a process called peristalsis, involuntary wavelike contractions of the colon wall. The fecal matter is then stored in the rectum, until it is expelled out of the anus through a bowel movement.

Colon Cancer

Cancer of the colon is known as colorectal cancer. It almost always begins as an abnormal growth of tissue called an intestinal polyp, or adenoma. Over 95% of colorectal cancers are adenocarcinomas that develop from a mutation in the cells lining the wall of the colon and/or rectum. The risk factors are:

• A history of ulcers in the large intestine
• History of colon, ovarian, rectal, endometrial, or breast cancer.
• Hereditary nonpolyposis colon cancer (HNPCC)
• Family history of colon cancer
• 50 years of age or more

Symptoms

Unfortunately, most people who have colon cancer have either very nonspecific symptoms or none at all; unless the cancer has become advanced, at which point any or all of the following symptoms may appear:

• Bloody and/or narrow stools
• Diarrhea
• Constipation
• Weight loss
• Fatigue
• Vomiting
• Gas pains and bloating
• Bowels do not feel empty after expelling waste.

Tumors in the ascending colon are able to grow unhindered because the stool in the ascending colon is very nearly liquid and is not obstructed by the growths. Symptoms of blocked bowel movements tend to show up first in the descending colon because the stool is more solid there.

Diagnosis

Tests that examine the rectum, rectal tissue, and blood are used to find and diagnose colorectal cancer. The following methods are used:

• Physical exam- The doctor does a general health check and looks for anything abnormal.
• Fecal occult blood test- A laboratory test of a stool sample to check for blood not visible to the naked eye.
• Digital exam- An examination by the doctor with a gloved and lubricated finger.
• Barium enema (also known as a “lower GI series”)-Barium is a silver-white metallic compound; it is added to liquid and put into the rectum. The lower intestinal tract is coated by the barium and a series of x-rays are taken.
• Sigmoidoscopy- A thin, lighted tube called a simoidoscope is inserted into the sigmoid colon to look for anything abnormal. Tissue samples may be harvested.
• Colonoscopy- An instrument similar to the sigmoidoscope is inserted in order to look inside the rectum and colon.
• Biopsy- Harvested cells retrieved from the other procedures are observed beneath a microscope.
• Doppler Ultrasound- The ultrasound measures the blood flow from the artery to the liver, as well as the total liver flow.

Stages

Before a treatment plan can be created or a prognosis suggested, the stage of the cancer must be determined. It is judged on whether the cancer is in the inner lining of the colon only, involves the whole colon, or has spread to other organs. The following tests and procedures are used for “staging” the cancer:

• Computerized Tomography (CT or CT scan) - Detailed images are created from X-ray transmissions via a data-synthesizing computer. A dye may be injected into a vein or swallowed whole to help the organs or tissues show up more clearly.
• Magnetic Resonance Imaging (MRJ) - The MRI uses a magnetic field instead of X-rays. Unlike the CT, there is no radiation involved and the MRI provides better pictures of tumors near the bone.
• Lymph node biopsy-the removal of all or part of a lymph node for observation under a microscope.
• Chest X-ray- An X-ray is a picture of the bones and organs on the inside of the chest, taken with a machine with an energy beam that can go through the body and onto film.
• Complete blood count (CBC)- Blood is checked for the number of red blood cells, white blood cells, platelets, hemoglobin (oxygen-carrying protein), and the percentage of red cells in comparison to the rest.
• Carcinoembryonic antigem (CEA) - Also a blood test, CEA is released into the bloodstream by healthy and cancerous cells. Elevated amounts can be a sign of colon cancer.
• Surgery- the doctor goes into your body to remove the tumor and to inspect the other organs to see if it has spread.

Staging

After all the test results have been examined, a final “pathologic” stage will be assigned. Sometimes it’s a number and sometimes it’s a letter; different staging systems are used in different places.

Stage 0 is also called carcinoma in situ. This is the earliest and best diagnosis as the cancer is found only in the innermost lining of the colon.

Stage I cancer has spread beyond the innermost lining of the colon wall into the middle layers.

Stage II cancer is divided into stages IIA and IIB. With IIA the cancer has spread beyond the middle tissue of the wall or spread to nearby tissues around the colon or rectum. IIB has spread beyond the colon wall and moved into nearby organs through the peritoneum (a transparent membrane that lines the abdominal cavity).

Stage III cancer is divided into 3 sub-stages. With IIIA the cancer has spread to the middle layers and 1-3 lymph nodes. The IIIB cancer has spread to 1-3 lymph nodes AND beyond the middle tissue of the colon wall, or beyond the wall into the organs, or to nearby tissues around the rectum or colon. Stage IIIC has spread to 4 or more lymph nodes AND beyond the middle tissue, or into the organs, or to nearby tissues around the rectum or colon.

Stage IV cancer is very advanced and carries the worst prognosis. There is a 5-year survival rate of less than 5% for people diagnosed at this late stage. Stage IV cancer has spread to other organs, often the liver, lungs, or bones, and may have spread to lymph nodes as well.

Recurrent cancer is cancer that has returned after an initial treatment.

In summary, Stage I indicates cancer in the most superficial layer of the bowel wall, Stage II has moved into the muscular wall, Stage III indicates cancer in the lymph nodes, Stage IV indicates spread to other sites, and recurrent cancer has returned.

Treatment

Medical science is constantly creating and designing new and hopefully better ways to deal with all types of cancer, including colorectal. Clinical trials are taking place in many parts of the country and world. In a clinical trial you become part of a research study testing up-and coming treatments. A lot of clinical trials take place at specific institutions or health care centers and require you to be there to participate. You will have to incur the travel costs if you choose to take part in something outside of your living area.

There are a lot of things to think about when considering such a trial, the location, the support system you have, the financial resources available to you, the stage of the cancer and its relative prognosis are a few. Ultimately each cancer patient’s situation and personal make-up are entirely unique so it’s best to consider yours carefully when deciding.

The standard treatments for each stage of colon cancer are as follow:

Stage 0 is treated with cryosurgery, also called cryotherapy. The abnormal cells are frozen and destroyed. If the cancer is found to be in the form of a polyp, a tube is inserted into the colon and the polyp is cut out. This operation is called a polypectomy. The 5-year survival rate for colon cancer diagnosed at this stage is near 100%, unless a recurrent cancer appears.

Stage I is treated with resection and anastomasis. Resection is the removal of the cancer and a small amount of healthy tissue around it. Anastomosis is a fancy medical word to say that the healthy parts of the colon are sewn back together.

Stage II treatment consists of resection/anastomosis and possibly chemotherapy, radiation, or biological therapy after surgery.

Chemotherapy uses drugs to stop the growth of cancer cells or kill them. The drugs are administered orally, intravenously (I.V.), shot-form, or directly into the spinal column.

Radiation treatment may be internal or external. With internal therapy a radioactive substance is placed directly into or near the cancerous site(s) via needles, wires, or catheters. External radiation uses a machine to send high-energy X-rays toward the cancer.

Biologic therapy is also called biotherapy or immunotherapy. Substances made by the body or made in the lab are used to boost and/or restore the body’s own natural defenses (immune system).

Stage III cancer is treated like Stage II cancer with a more aggressive approach. Possibly varied chemotherapy drugs and/or different doses.

Stage IV cancer is treated with resection/anastomosis, surgery, clinical trials, radiation and/or chemotherapy.

There are special treatments for cancer that has spread or recurred to the liver. Radiofrequency ablation is done with a special needle that releases tines (tiny cancer-killing electrodes) into the cancer. This can be done with local anesthesia when the needle is inserted directly into the skin. If it needs to be inserted through an incision in the abdomen, general anesthesia is used.

Hepatic chemoembolization with radiation therapy is under clinical trial. The hepatic artery is the main supplier of blood to the liver. In chemoembolization the artery is blocked and chemotherapy drugs are injected in between the liver and the blockage. The liver’s arteries deliver the drug throughout the liver. The hepatic portal vein, which carries blood from the intestine and stomach, continues to send some blood to the liver, so it is not entirely cut off.

Cryosurgery (definition above) can also be used in conjunction with these treatments.

Prognosis

The long-term outlook at the chance of survival after therapy is called the prognosis. Survival rates are greatly increased with early detection.

The overall 5-year survival rate from colon cancer is approximately 60%. Stage 0 and Stage I cancers have a 5-year survival rate of over 90%. Stage II and III cancers have a survival rate of between 70-85% depending on whether the cancer has spread out to other areas or not. If the tumor spreads to the lymph nodes, the 5-year survival rate is less than 60%. Recurrent cancer has a poor prognosis, with an only 5% survival rate.

Prevention

There are several things a person who wishes to decrease their likelihood of developing colon cancer can do.

• Take aspirin on a daily basis. Aspirin interferes with prostaglandin metabolism which is thought to be the reason it reduces the risk of colon, stomach, and esophagus cancer, as well as cardiovascular disease. One coated adult aspiring (325mg) is considered adequate. Despite its usefulness in the quest for preventing colon cancer, it must be noted that aspiring can cause ulcers and bleeding, among other things.)
• Quit smoking.
• Supplement the calcium in your diet. The general recommendation is 1500 mg or more a day, but talk to your doctor about the right amount for you.
• Exercise daily.
• Lose any extra weight.

Of course, doing all these things will not guarantee exemption from colorectal cancer, but it is certainly worth the time to lower your risk factors. Besides getting daily exercise, quitting smoking, and losing excess weight will decrease the risks of many other diseases and potentially fatal illnesses too. Know your body and trust your judgment; if you think something is wrong, go to the doctor. Always remember, it is better to be a hypochondriac than a corpse.