Introduction:
Colon cancer is a form of cancer that starts in the large intestine, the colon, which is the last part of the digestive tract. Colon cancer usually affects the older population, though it can occur at any age. It usually starts as small clumps of cells called polyps that are non-cancerous and form within the colon. With time some of these growths or polyps can become cancerous. These polyps are relatively small and may or may not produce a few symptoms. It is recommended to undergo regular screening tests to prevent colon cancer by finding and removing the polyps before they turn cancerous. Several treatment options are available to control colon cancer, including surgery, radiation therapy, and certain drug treatments, such as targeted therapy, chemotherapy, and immunotherapy. Colon cancer is sometimes called colorectal cancer, which combines both colon and rectal cancer and begins in the rectum.
What Are the Risk Factors of Primary Colon Cancer?
Several risk factors have been identified to cause primary colon cancer; they include the following:
-
Low fiber and high fat and animal protein diet.
-
Inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis.
-
Exposure to asbestos.
-
Family history of benign or malignant cancers.
-
Pelvic irradiation.
-
A history of breast or endometrial cancers.
-
Ureterosigmoidostomy (a surgical procedure that involves creating a connection between the ureter and the sigmoid colon to manage urinary dysfunction).
-
Colon dysplasia (a condition characterized by abnormal growth and development of cells in the lining of the colon).
-
Lymphoid follicles.
-
Colon adenoma (a type of polyp or growth that can develop in the colon).
What Causes Primary Colon Cancer?
It is not known what leads to colon cancer. Colon cancer begins when the healthy colon cells develop alterations or mutations in their DNA (deoxyribonucleic acid). The DNA of a cell harbors the hereditary components of the body. These healthy cells grow and divide in a set order to keep the normal functioning of the body going. But when the DNA of a cell becomes cancerous, the cells continue to divide uncontrollably. As a result, these cells keep on accumulating, forming a tumor. As cancer progresses with time, the cancerous cells grow further, invading and destroying the nearby healthy tissues. This invasion of the cancerous cells to other body parts is known as metastasis.
What Are the Symptoms of Primary Colon Cancer?
The various symptoms include the following:
-
A change in bowel habit (constipation or diarrhea).
-
Iron deficiency anemia due to blood loss.
-
Bowel obstruction.
-
Heavy rectal bleeding.
-
Intussusception.
Less common symptoms include the following:
-
Respiratory symptoms because of metastasis to the lungs.
-
Paraneoplastic syndromes such as dermatomyositis (inflammation of the skin, which can cause a distinctive rash, as well as weakness and inflammation of the muscles).
-
Bacteremia (spread of bacteria into the bloodstream) or bacterial endocarditis.
How Is Primary Colon Cancer Diagnosed?
Primary colon cancer can be diagnosed through thorough physical examination, blood tests, and screening tests. A regular screening test can detect cancer before the symptoms develop and is often curable.
The doctor will perform a thorough physical examination of the abdomen by pressing on the belly. The physical examination rarely shows any problems; sometimes, the doctor might feel a lump in the abdominal area. A rectal examination might detect a lump in individuals with rectal cancer but not colon cancer. Certain tests used for screening for colon cancer include the following:
-
Sigmoidoscopy - A test to check the lower part of the colon.
-
Colonoscopy - Full colonoscopy can view the complete colon. This is one of the best screening tests for colon cancer.
-
Complete Blood Count - To detect iron deficiency anemia.
-
Liver Function Test - To detect the elevated levels of certain liver enzymes.
-
Carcinoembryonic Antigen Test (CEA) - A blood protein that is elevated in colon cancer.
If one is diagnosed with colorectal cancer, more tests will be required to see if the cancer has spread. These tests are called staging. For staging, CT (computed tomography), MRI (magnetic resonance imaging), or PET (positron emission tomography) scans of the abdomen, pelvic area, or chest are done. The various stages of colon cancer are as follows:
1. Stage 0: Earliest cancer stage on the innermost layer or mucosa of the intestine.
2. Stage I: Cancer has spread to the inner layers (mucosa, submucosa) of the colon.
3. Stage II: Cancer has spread beyond the mucosa and the submucosal layer of the colon. It is further classified into the following:
-
Stage II A - Cancer has not spread to the lymph nodes or the nearby tissues. It has spread to the outer layers of the colon.
-
Stage II B - Cancer has not spread to the lymph nodes, but it has spread through the outer layers of the colon and to the visceral peritoneum (the membrane that holds the abdominal organs together in place).
-
Stage III C - Cancer has not spread to the lymph nodes. But it has spread through the outer layer of the colon as well as to adjoining organs or structures.
4. Stage III: Cancer has spread to the nearby lymph nodes. It is further classified into the following:
-
Stage III A - The tumor has spread through the muscular layers of the colon and has spread to the nearby lymph nodes. It has not spread to the farther lymph nodes or organs.
-
Stage III B - Colon cancer can be classified under stage III B either if the tumor has spread through the colon's outermost layers (mucosa) and penetrates the visceral peritoneum or spreads to other organs or structures. Or if the tumor has not spread through the outermost layers of the colon but is found in four or more adjacent lymph nodes.
-
Stage III C - The tumor has spread beyond the muscular layers and is also found in four or more nearby lymph nodes but not farther.
5. Stage IV: Cancer has spread to other organs outside the colon. It is further classified into the following:
-
Stage IV A - Cancer has spread to at least one distant organ, like the liver, lungs, or lymph nodes.
-
Stage IV B - Cancer has spread to two or more distant organs but not to the peritoneum (the tissue that lines the various abdominal organs).
-
Stage IV C - Cancer has spread to the peritoneum.
How Is Primary Colon Cancer Treated?
Primary colon cancer can be treated by various treatment modalities, depending on the location and spread of the cancer.
The following are the treatment modalities:
-
Surgery - The cancerous part of the colon is surgically removed. Keyhole or robotic surgery can be done for quick recovery and less pain.
-
Chemotherapy - In chemotherapy, medication is used to kill cancerous cells.
-
Radiation Therapy - Radiation is used to kill cancer cells. It is usually done after chemotherapy.
-
Targeted Therapy - Targeted therapy is done by a group of medications that prevents cancer from spreading.
A complete cure for cancer depends upon its spread. In the case of primary colon cancer, in which the cancer is confined to the colon and not spread across, surgery can remove it completely.
Conclusion:
Colon cancer develops from the uncontrolled growth of cells in the inner lining (mucosa) of the colon. Various screening tests and treatments detect and remove precancerous colon polyps. If left untreated, colon cancer may spread to other parts of the body. Early diagnosis and prompt treatment are key to preventing cancers from spreading.
