Colon Cancer is a disease afflicting humans and is a malignant tumor, which arises from the inner wall of the large intestine (colon), or the rectum (which is the end of the colon). It is also referred to as colorectal cancer. In the United States, it is the third leading cause of cancer in males, and fourth in females.

The human colon is a tube shaped muscular organ which is about four feet in length, extending from the small bowel to the anus. It has three main functions, which are digest and absorb nutrients from the food, to concentrate fecal material by absorbing fluids, and store fecal material and control its evacuation.

Colon

Normally cells divide and multiply only when our bodies need them to do so. When normal cells transform and grow and multiply in an abnormal manner, they form a mass of tissue, which is called a growth or tumor. This can either be malignant or benign. They do not extend to other parts of the body, and therefore can be removed, and rarely recur.

However, malignant tumors are cancer, and the cells can invade and spread to other tissues and organs of our body. These cells can also break away from the tumors and enter the blood stream, thereby spreading to other parts of the human body. When such spread occurs it is termed as ‘metastases.

Polyps are the benign tumors of large intestine, while the ones which are malignant are known as cancers. Benign polyps are not life frightening, and can be detached at some point in colonoscopy. However, if these are not removed, they can turn malignant (cancerous) over time. Once these cells spread to other parts of the body; (i.e. metastasis has occurred), a complete cure of the cancer is unlikely.

Causes of Colon Cancer

There is no single cause of colon cancer. While colon cancer is not contagious, some people are more likely to get afflicted by colon cancer than the others. While the disease is common in the Western World, it is rare Asians and Africans. Doctors believe that people having diets high in fat are more prone to developing colon cancer, as countries with higher instances of colon cancer consume higher amount of fat in their diet. The breakdown products of fat metabolism cause the formation of carcinogens, which are cancer causing chemicals. Consumption of vegetables and food rich in fiber content, such as whole grain cereals and breads may reduce the risk as they rid the bowel of these harmful carcinogens.

The genetic background of a person also determines the risk of him developing colon cancer, though about 80 percent of the cases are found to occur in people who have no family history of the disease.

The risk of developing colon cancer is higher in people having cancer elsewhere in their body, and also where people have ulcerative colitis.

Symptoms of Colon Cancer

Though symptoms do not appear in many cases of colon cancer, the following symptoms may indicate its occurrence:

  • Abdominal Pain and tenderness in the lower abdomen
  • Constipation, diarrhea, or change in bowel movements such as narrow stools
  • Unexplained Anemia
  • Passing blood in stools
  • Weight loss in some cases

If colon cancer is detected before the symptoms occur, then it is easily cured.

Detection of Colon Cancer

When a person is suspected to have colon cancer, either a Gastro Intestinal series (Barium Enema X ray) or a colonoscopy is performed. In Barium Enema, the patient is given an enema containing barium in a white liquid, and an x ray of the colon is taken. In case tumors exist, they appear as dark shadows on the x ray.

Colonoscopy is another popular procedure, in which a long and flexible tube is inserted into the rectum enabling the doctors to inspect the inside of the colon. If polyps are found, these are removed using the colonoscope and the tissue samples (biopsies) of the polyps thus obtained are then examined under the microscope for diagnosis.

If colon cancer is confirmed, staging examinations are performed in order to determine whether the cancer has spread to other organs of the body. Staging tests normally include x rays of the chest, ultrasonography, or at times a CAT SCAN of the abdomen, liver and lungs. In some cases, the doctors may carry out a blood test to detect carcinoembyonic antigen, or CEA which is a substance produced by certain cancer cells.

A stool occult blood test is an important test for screening cases of colon cancer, wherein the stools of a suspected patient is examined for traces of blood. In only about 45 % of cases when a person tests positive for stool occult blood has a colon polyp, and only about 5% have a chance of having colon cancer. However, about 20 % chances of colon cancer going undetected when performing stool occult blood test remain, and these are confirmed by sigmoidoscopies (A short version of colonoscopy) or colonoscopies.

Prevention of Colon Cancer

It is beneficial for people with high risk of colon cancer to increase intake of fibrous foods, such as vegetables, fruits, wholegrain cereals and breads. As fibers are the insoluble and non digestible parts of plant material, they can help rid the colon of carcinogens, thus reducing risk.

Staging

When occurrence of colon cancer is confirmed, tests are done to determine the spread, called staging:

Stage 0 – Very Early stage with cancer of the innermost layer of the colon
Stage I – Cancer in the inner layers of the colon.
Stage II – When the cancer has spread through the muscle wall of the colon.
Stage III – When cancer has spread to lymph nodes.
Stage IV – When cancer has spread to other organs of the body.

(Authority: MEDLINE PLUS, A service of the Us National Library of medicine and the National Institutes of Health)

Treatment Options by Stage

The treatment varies depending on the stage, and includes surgery to remove cancer cells, chemotherapy medicines to kill the cancerous cells and radiation therapy to destroy cancerous tissue. While Stage 0 cancer can be treated by removing the cancer cells, for other stages, more extensive surgery is required. Almost all patients with Stage III colon cancer should undergo Chemotherapy (drug 5-fluorouracil) for six to eight months, which increases the chances of cure.

Oxaliplatin, Irinotecan, and 5-fluorouracil are the Chemotherapy drugs used to treat patients with Stage IV colon cancer.

In cases when Stage IV colon cancer has spread to the liver, treatments such as cutting out the cancer, burning it (ablation), or freezing it (cryotherapy), or chemotherapy and occasionally, radiation therapy.

Surgery for Colon Cancer

Surgery is the cornerstone for treatment of colon cancer, and may involve removal of the colon in part or full, depending on the characteristics of the tumor. At times surgery is also done when a bowel obstruction occurs, and is usually a bypass when the obstruction cannot be cured or removed.

Surgical Procedure

Sometimes a case of colon cancer can only be surgically removed by creation of a permanent colostomy, depending on the circumstances. This is a small opening in the belly, and the remaining part of the colon is attached to this opening. Fecal matter will be discharged through this opening instead of the anus.
Generally, tumors on the right side of the colon or on the left side above the level of the rectum may not warrant colostomy.

Additional reading:

Types of Skin Cancer
Skin Cancer Treatment

References:

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