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Information About Colon Cancer
By peace | December 24, 2006
Globally, cancer of the colon and rectum is the third leading cause of cancer in males and the fourth leading cause of cancer in females. The frequency of colorectal cancer varies around the world. It is common in the Western world, and is rare in Asia and Africa. In countries where the people have adopted western diets, the incidence of colorectal cancer is increasing.
Symptoms of colon cancer
Symptoms of colon cancer are numerous and non-specific. They include fatigue, weakness, shortness of breath, change in bowel habits, narrow stools, diarrhea or constipation, red or dark blood in stool, weight loss, abdominal pain, cramps, or bloating. Other conditions such as irritable bowel syndrome (spastic colon), ulcerative colitis, Crohn’s disease, diverticulosis, and peptic ulcer disease can have symptoms that mimic colorectal cancer.
Colon cancer can be present for several years before symptoms develop. Symptoms vary according to where in the large bowel the tumor is located. The right colon is spacious, and cancers of the right colon can grow to large sizes before they cause any abdominal symptoms. Typically, right-sided cancers cause iron deficiency anemia due to the slow loss of blood over a long period of time. Iron deficiency anemia causes fatigue, weakness, and shortness of breath. The left colon is narrower than the right colon. Therefore, cancers of the left colon are more likely to cause partial or complete bowel obstruction. Cancers causing partial bowel obstruction can cause symptoms of constipation, narrowed stool, diarrhea, abdominal pains, cramps, and bloating. Bright red blood in the stool may also indicate a growth near the end of the left colon or rectum.
Colon polyps and colon cancer
Doctors believe that most colon cancers develop in colon polyps. Therefore, removing benign colon polyps can prevent colorectal cancer. Colon polyps develop when chromosome damage occurs in cells of the inner lining of the colon. Chromosomes contain genetic information inherited from each parent. Normally, healthy chromosomes control the growth of cells in an orderly manner. When chromosomes are damaged, cell growth becomes uncontrolled, resulting in masses of extra tissue (polyps). Colon polyps are initially benign. Over years, benign colon polyps can acquire additional chromosome damage to become cancerous.
Ulcerative colitis and colon cancer
Chronic ulcerative colitis causes inflammation of the inner lining of the colon. The risk of colon cancer is much higher than average for patients with chronic ulcerative colitis of long duration. The risk of colon cancer increases significantly after 10 years of colitis.
Genetics and colon cancer
A person’s genetic background is an important factor in colon cancer risk. Among first-degree relatives of colon cancer patients, the lifetime risk of developing colon cancer is eighteen percent (a threefold increase over the general population in the United States).
Even though family history of colon cancer is an important risk factor, majority (80%) of colon cancers occur sporadically in patients with no family history of colon cancer. Approximately 20% of cancers are associated with a family history of colon cancer. And 5 % of colon cancers are due to hereditary colon cancer syndromes. Hereditary colon caner syndromes are disorders where affected family members have inherited cancer causing genetic defects from one or both of the parents.
Chromosomes contain genetic information, and chromosome damages cause genetic defects that lead to the formation of colon polyps and later colon cancer. In sporadic polyps and cancers (polyps and cancers that develop in the absence of family history), the chromosome damages are acquired (develop in a cell during adult life). The damaged chromosomes can only be found in the polyps and the cancers that develop from that cell. But in hereditary colon cancer syndromes, the chromosome defects are inherited at birth and are present in every cell in the body. Patients who have inherited the hereditary colon cancer syndrome genes are at risk of developing large number of colon polyps, usually at young ages, and are at very high risk of developing colon cancer early in life, and also are at risk of developing cancers in other organs.
FAP (familial adenomatous polyposis) is a hereditary colon cancer syndrome where the affected family members will develop countless numbers (hundreds, sometimes thousands) of colon polyps starting during the teens. Unless the condition is detected and treated (treatment involves removal of the colon) early, a person affected by familial polyposis syndrome is almost sure to develop colon cancer from these polyps. Cancers usually develop in the 40’s. These patients are also at risk of developing other cancers such as cancers in the thyroid gland, stomach, and the ampulla (the part where the bile ducts drain into the duodenum just beyond the stomach).
AFAP (attenuated familial adenomatous polyposis) is a milder version of FAP. Affected members develop less than 100 colon polyps. Nevertheless they are still at very high risk of developing colon cancers at young ages. They are also at risk of having gastric polyps and duodenal polyps.
HNPCC (hereditary nonpolyposis colon cancer) is a hereditary colon cancer syndrome where affected family members can develop colon polyps and cancers, usually in the right colon, at early ages of 30’s to 40’s. Certain HNPCC patients are also at risk of developing uterine cancer, stomach cancer, ovarian cancer, and cancers of the ureters (the tubes that connect the kidneys to the bladder), and the biliary tract (the ducts that drain bile from the liver to the intestines).
MYH polyposis syndrome is a recently discovered hereditary colon cancer syndrome. Affected members typically develop 10-100 polyps occurring at around 40 years of age, and are at high risk of developing colon cancer.
Fast Facts About Colon Cancer
- Colorectal cancer is a malignant tumor arising from the inner wall of the large intestine.
- Colorectal cancer is the third leading cause of cancer in males, fourth in females in the U.S.
- Risk factors for colorectal cancer include heredity, colon polyps, and long standing ulcerative colitis.
- Most colorectal cancers develop from polyps. Removal of colon polyps can prevent colorectal cancer.
- Colon polyps and early cancer can have no symptoms. Therefore regular screening is important.
- Diagnosis of colorectal cancer can be made by barium enema or by colonoscopy with biopsy confirmation of cancer tissue.
- Treatment of colorectal cancer depends on the location, size, and extent of cancer spread, as well as the age and health of the patient.
- Surgery is the most common treatment for colorectal cancer.
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