Abstract Colorectal cancer, more commonly known as colon cancer, is a common form of cancer. It is the third most common type of cancer and the second most lethal. It is fairly common due to the numerous causes and contact with foreign substances. Cancer is the condition of where cells do not cease mitosis, and continue to duplicate in tumors. If the cancer cells do not metastasize, spread to other parts of the body, they are said to be benign. Benign tumors are not extremely harmful until they metastasize and become malignant.
Colorectal cancer can be located either in the rectum or colon. The stages range from I to IV, with I being the least advanced and harmful to IV being the worst, as it has metastasized. Symptoms include blood in the stool or change in bowel habits. Screening is with fecal occult blood testing. Diagnosis is by colonoscopy. Treatment is surgical resection and chemotherapy for nodal involvement. It can be cured if it is caught early enough. Incidence Colorectal cancer accounts for an estimated 153,000 cases and 52,000 deaths in the US annually.
In Western countries, the colon and rectum account for more new cases of cancer per year than any anatomic site except the lung. Incidence begins to rise at age 40 and peaks at age 60 to 75. Overall, 70% of cases occur in the rectum and sigmoid, and 95% are adenocarcinomas. Colon cancer is more common among women; rectal cancer is more common among men. Synchronous cancers (more than one) occur in 5% of patients. Etiology: Colorectal Cancer (CRC) most often occurs as transformation within adenomatous polyps. Serrated adenomas are aggressive particularly in their malignant transformation.
About 80% of cases are sporadic, and 20% have an inheritable component. Predisposing factors include chronic ulcerative colitis and granulomatous colitis; the risk of cancer tends to increase with the duration of these disorders. Populations with a high incidence of CRC diets tend to be low in fiber but high in animal protein, fat, and refined carbohydrates. Carcinogens may be ingested in the diet but are more likely to be produced by bacterial action on dietary substances or biliary or intestinal secretions. The exact mechanism is not known for sure.
CRC spreads through the bowel wall by direct extension, hematogenous metastasis, regional lymph node metastasis, perineural spread, and intraluminal metastasis. Quite a few things contribute to this condition. The risk increases with time and a family history of colon cancer. Women are less likely to get it than men, with African-American men having the highest risk in the United States. Physically inactive people and smokers tend to have higher risk. Diets that are high in fiber and red meat are more risky, fruits and vegetables are the best diet to avoid CRC.
Hereditary conditions increasing the risk of colon cancer include a general family history, Familial adenomatous polyposis, and Hereditary nonpolyposis colorectal cancer. Familial adenomatous polyposis increases the risk of developing colon cancer to almost certain. The disorder causes a person to have thousands of polyps, causing anemia from an early age due to loss of blood in the feces. Later the person will most likely develop cancer. Hereditary nonpolyposis colorectal cancer is also called Lynch Syndrome. Lifetime risk is approximately 80%, it also increase risks of numerous other cancer in the digestive tract as well.
Symptoms and Signs: Symptoms may be full on and complete or could be nearly nonexistent. Symptoms include a change in bowel patterns, blood in feces, and bowel obstruction by the tumor. Blood is usually the best indicator because it is specific to colon cancer. Bowel obstruction is fairy rare, other symptoms would usually show before this. Other symptoms that are not necessarily associated with colon cancer include weight loss, anemia, and enlargement of the liver. Colorectal adenocarcinoma grows slowly, and a long interval elapses before it is large enough to cause symptoms.
Symptoms depend on lesion location, extent, type, and complications. The right colon has a large caliber, a thin wall, and its contents are liquid. Fatigue and weakness caused by severe anemia may be the only complaints. Tumors sometimes grow large enough to be palpable through the abdominal wall before other symptoms start appearing. The left colon has a smaller lumen, the feces are semisolid, and cancer tends to encircle the bowel, causing alternating constipation and increased stool frequency or diarrhea. Partial obstruction with colicky abdominal pain or complete obstruction may be the initial sign.
The stool may be streaked or mixed with blood. In rectal cancer, the most common initial symptom is bleeding with defecation. Whenever rectal bleeding occurs, even with obvious hemorrhoids or known diverticular disease, coexisting cancer must be ruled out. Tenesmus or a sensation of incomplete evacuation may be present. Pain is common with perirectal involvement. Diagnosis: Early diagnosis depends on routine examination, particularly fecal occult blood (FOB) testing. Cancer detected by this method tends to be at an earlier stage and hence more curable.
For average-risk patients, FOB testing should be done annually after age 50, with flexible sigmoidoscopy every 5 yr. Some authorities recommend colonoscopy every 10 yr instead of sigmoidoscopy. Colonoscopy every 3 yr may be even better. CT colonography (virtual colonoscopy) generates 3D and 2D images of the colon using multidetector row CT and a combination of oral contrast and gas distention of the colon. It has some promise as a screening test for people who are unable or unwilling to undergo endoscopic colonoscopy but is less sensitive and highly interpreter dependent.
It avoids the need for sedation but still requires thorough bowel preparation, and the gas distention may be uncomfortable. Additionally, unlike with optical colonoscopy, lesions cannot be biopsied during the diagnostic procedure. Video capsule endoscopy of the colon has many technical problems and is not currently acceptable as a screening test. All lesions should be completely removed for histologic examination. If a lesion is sessile or not removable at colonoscopy, surgical excision should be strongly considered.
Barium enema x ray, particularly a double-contrast study, can detect many lesions but is somewhat less accurate than colonoscopy and is not preferred as follow up to a positive FOB test. Once cancer is diagnosed, patients should have abdominal CT, chest x ray, and routine laboratory tests to seek metastatic disease and anemia and to evaluate overall condition. The length of time needed to develop colon cancer is long enough so the best medicine is early diagnosis, so there are numerous ways to diagnose.
Screening can be done by fecal occult blood test, sigmoidoscopy, colonoscopy, and virtual colonoscopy. Colonoscopies are by far the most popular to diagnose with, as it is a lighted probe that can also remove polyps during the procedure. It is similar to a sigmmoidoscopy, although it only goes into the lower colon and can not remove polyps. Virtual colonoscopy is a noninvasive procedure that uses x-rays to find colon cancer. The effectiveness of it is getting better but is not at the level of a real colonoscopy. The fecal blood test less useful because it can find polyps but it can be an indicator of colon cancer.
Genetic or hereditary testing will help find out if a person has a disorder linked to colon cancer or if they have a general predisposition. Discovering malignancy is done using different procedures. Blood tests can detect the levels of certain proteins which may indicate metastasizing. Positron emission tomography uses radioactive sugar injected into the body that in conjunction with 3d imaging can show where the malignant, metabolically active cancer cells are. Digital rectal exam can find tumors that are large enough to be felt.
Standard computed axial tomography uses 3d computer imaging to find the extent of spread cancer. It is not sensitive enough to find polyps. Treatment: The first way to treat colon cancer is by surgery. This is for cancer that has not metastasized yet. A colonoscopy can be done for the earlier stages but after the cancer has developed enough, deeper surgery must be used. Usually this involved taking out part of the colon and fusing together the remaining parts. The most common treatment is resection of the index lesion with frequent surveillance for another colon cancer and any associated tumors in other organs.
Because most HNPCC tumors occur proximal to the splenic flexure, subtotal colectomy, leaving the rectosigmoid intact, has been suggested as an alternative. Rare complications include infection, abscess, fistula or bowel obstruction. Radiation therapy uses radiation to kill cancer cells. It may be used in conjunction with surgery or chemotherapy. There are some remedies but they are unproven but probably won’t do any harm. They include ginger, curcumin, mistletoe extract, and acupuncture. Chemotherapy is still the most effective for malignant cancers.
Usually this takes place after surgery to stop any metastasis from occurring. It can also be used by itself or at other times, like before surgery. Literature Cited: Altman, Roberta. The Cancer Dictionary. New York: Fact On File Inc. , 1992. Anderson, Greg. 50 Essential Things to Do When The Doctor Says It’s Cancer.
New York: The Penguin Group, 1993. Livstone,Elliot M. . (December, 2007 ). Colorectal Cancer. In The Merck Manual for Healthcare Professionals. Retrieved july 25,2011, from http://www. merckmanuals. com/professional/sec02/ch021/ch021g. html#v895979.