Before answering what is colon cancer, it is best to define the function of the colon and the rectum. The colon is part of the digestive system that stores waste materials. The rectum is the end of the colon close to the anus. The colon and rectum form the large intestine which is also known as the large bowel.
Colon cancer, also known as colorectal cancer, refers to malignant growths in the colon, rectum, and the appendix. After lung cancer, prostate and breast cancer, it is the third most leading causes of cancer related deaths. Colon cancers arise from adenomatous polyps in the colon. Such growths arising from the inner wall of the large intestine are usually benign in nature but may develop into cancer over time. Benign polyps are not life threatening and can be easily removed during colonoscopy. They do not invade nearby tissues or metastasize to other parts of the body. Cancer of the colon and rectum can damage nearby tissues and organs. It may also metastasize to the liver and lungs forming new tumors. When cancer has spread to distant parts from the colon and rectum area, it is rather unlikely for the cancer to be cured.
Age is a risk factor for developing colorectal cancer as most cases occur in people aged 60 to 70. Adenomatous polyps of the colon may develop into cancer over time. Removal during colonoscopy reduces the risk. Individuals diagnosed and treated with colon cancer or cancers of other forms are at risk of developing colorectal cancer in the future. A family history of colon cancer increases one’s risk. Smokers are more likely to die of colorectal cancers than those who don’t smoke. Diets rich in red meat and poor in fruits, vegetables, poultry and fish are more prone to colorectal cancer. Physical inactivity increases the risk of developing colorectal cancer. Exposure to viruses like HPV may be associated with colorectal cancer. Low levels of selenium increases the risk of developing colorectal cancer. Inflammatory bowel diseases are sometimes associated with colorectal cancer. Environmental factors also pose a risk such that industrialized countries are at relatively higher risk compared to less developed countries. Exogenous hormones such as exposure to estrogens might be associated with colorectal tumors. Heavy alcohol intake is a risk factor.
Symptoms depend on the location and extent of the tumor. Colon cancer may be present for a long time before symptoms develop. Because the right colon is spacious, cancers may grow o large sizes before they show abdominal symptoms. Right-sided colorectal cancers cause iron deficiency anemia caused by loss of blood over a long period of time. Cancers to the left of the colon more likely causes bowel obstruction. Bright red blood in the stool may indicate presence of cancer near the end of the left colon or rectum. Symptoms are divided into local, constitutional (affecting the entire body), and metastatic (cause by spread to other organs).
Local symptoms usually appear if the tumor is located closer to the anus. Change in bowel movement (constipation or diarrhea), incomplete defecation (tenesmus), and change of stool shape are characteristics of rectal cancer. Lower gastrointestinal bleeding may indicate colorectal cancer. Melena, as a result of upper gastrointestinal bleeding may also indicate colorectal cancer. Large tumors can block bowel and cause constipation, abdominal pain, abdominal distension and vomiting. More advanced tumors can become noticeable upon feeling the abdomen. Larger tumors may invade the bladder or the female reproductive tract resulting to blood or air in the urine or vaginal discharge for females.
Constitutional symptoms appear if a tumor has lead to chronic occult bleeding resulting to iron deficiency anemia. It may be characterized by fatigue, palpitations, and pale skin. Colorectal cancer may lead to weight loss due to a decrease in appetite. Other constitutional symptoms are unexplained fever and paraneoplastic syndrome, the most common being thrombosis.
Metastatic symptoms occur most commonly when the cancer has spread to the liver. Symptoms include jaundice, abdominal pain, and pale stools.
What is colon cancer’s diagnostic method? A lower GI series (barium enema x-ray) or colonoscopy may be performed to diagnose and localize colon cancer. A barium enema involves x-rays of the colon and rectum after enema with liquid called barium. The barium outlines the large intestine on the x-rays making tumors and other abnormalities appear like dark shadows on the x-rays. Colonoscopy involves insertion of a long, flexible tube into the rectum to inspect the inside of the entire colon. Colonoscopy is considered more accurate than barium enema x-rays, especially in finding small polyps. Colon polyps may be removed through the colonoscope and sent to the pathologist for examination. Although majority of the polyps are benign, many are precancerous which is why removal of precancerous polyps prevents future development of colon cancer.
Findings on cancerous growths are achieved during colonoscopy. Upon confirmation of colon cancer, a biopsy is performed to identify the cancer stage. Since colon cancers are known to extent to the liver and lungs, tests may include chest x-rays, ultrasonography, or CAT scan of the liver, lungs, and abdomen.
Sometimes, doctors may conduct tests in search for CEA (carcinoembyonic antigen) which is a substance produced by some cancer cells. High levels are sometimes found in colorectal cancer patients especially when the disease has spread.
What is colon cancer’s treatment? Surgery is the most common treatment for colon cancer. The tumor, a small margin surrounding the healthy bowel, and adjacent lymph nodes are removed in surgery. After removal, the surgeon reconnects the healthy sections of the large intestine. For rectal cancer patients, the rectum is permanently removed. Colostomy is the process wherein the surgeon creates an opening on the abdomen wall through which solid waste in the colon is excreted. Most patients with colostomies regain a normal lifestyle.
What is colon cancer patient faced with? Clear understanding of the causes and course of the disease is important; especially that colon cancer remains to be a major cause of cancer related deaths. Early detection can increase chances for cure and survival. Removal of colon polyps even prevents colon cancer. Treatment for more advanced colon cancers remains unsatisfactory but research is ongoing and new treatments continue to come out. Cancer patients are not faced with simple battles and need a social support system that will be with them through the entire diagnostic and treatment process.
