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Table of Contents

Magill’s Medical Guide, 9th Edition

Colorectal cancer

by Rodney C. Mowbray

Category: Disease/Disorder

Also known as: Large bowel cancer

Anatomy or system affected: Abdomen,,, gastrointestinal system, intestines, lymphatic system

Specialties and related fields: Gastroenterology, genetics, immunology, oncology, proctology, colorectal surgery

Definition: Cancer occurring in the large intestine.

Key terms:

polyp: an abnormal tissue growth that forms on the lining of the colon; may be benign or malignant

colonoscopy: a method of visualizing the colon using a camera attached to a flexible tube

hematochezia: bright red blood in stool, suggestive of a lower gastrointestinal bleed

melena: dark, black blood in stool suggestive of an upper gastrointestinal bleed or blood that has passed slowly through the GI system

CAUSES AND SYMPTOMS

With an estimated 51,000 deaths per year in the United States, cancer of the colon and rectum is the second most deadly cancer for both men and women, ranking only behind lung cancer. While mortality from colorectal cancer (CRC) has been declining, incidence among people less than 50 years old has been increasing over the last decade.

About 90 percent of colorectal cancers arise from the glandular epithelium lining the inner surface of the large bowel and are termed adenocarcinomas. The cells of the epithelial layer are constantly being replaced by new cells. This fairly rapid cell division, along with the relatively hostile environment within the bowel, promotes internal cellular errors that lead to the formation of aberrant cells. These cells can become disordered and produce abnormal growths or tumors. Often, colorectal tumors protrude into the lumen (the spaces within the bowel), forming growths called polyps. Some polyps are benign and do not spread to other parts of the body, but they may still disturb normal bowel functions. Other polyps become malignant by forming more aggressive cell types, which allows them to grow larger and spread to other organs. The cancer can grow through the layers of the colon wall and extend into the body cavity and nearby organs such as the urinary bladder. Cancer cells can also break away from the main tumor and spread (metastasize) through the blood or lymphatic vessels to other organs, such as the lungs or liver. If not controlled, the spreading cancer eventually causes death by impairment of organ and system functions.

The tendency to develop colorectal polyps and cancer can be inherited; this genetic predisposition may be responsible for about 5 to 7 percent of all colorectal cancers. One example is an inherited disorder called familial adenomatous polyposis (FAP), in which hundreds of polyps develop in the colon; it often leads to colorectal cancer. Some of the defective genes that cause this and other types of colorectal cancers have been identified and are being studied to determine their pathogenic role. Inflammatory bowel disease (IBD) and exposure to certain carcinogens, such as tobacco, as well as modifiable factors such as obesity and excessive alcohol consumption are also known to increase the risk of CRC.

Information on Colorectal Cancer

Causes: Hereditary and/or environmental factors, dietary habits, colon polyps, long-standing ulcerative colitis

Symptoms: 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, bloating

Duration: Chronic

Treatments: Surgery, chemotherapy, radiation

Symptoms of CRC can be highly variable. Many patients may be asymptomatic in early stages, with cancer being detected only through screening methods. Some of the most frequent signs and symptoms include hematochezia, melena, change in bowel habits, and shortness of breath or fatigue suggestive of iron-deficiency anemia. Of note, an iron-deficiency anemia in an older patient is suspect for a GI bleed until proven otherwise. Right-sided colon cancers typically present with bleeding and anemia while left-sided colon cancers typically present with obstructive symptoms including changes in bowel habits and abdominal pain.

TREATMENT AND THERAPY

The chances for survival are greatly increased when colorectal cancer is detected and treated at an early stage. The decline in mortality from CRC is attributed to early screening and detection. Early detection in the general population is possible with a number of methods: Digital rectal examination, in which the physician checks the inner surface of the rectal wall with a gloved finger for abnormal growths; fecal occult blood test, in which a stool sample is tested for hidden blood that may have emanated from a cancerous growth; sigmoidoscopy, in which the physician examines the rectal and lower-colon inner lining with a narrow tubular optical instrument inserted through the anus; colonoscopy, in which an optical instrument, inserted through the anus, assesses more of the colon and can remove tissue for pathological examination; virtual colonoscopy, which is a noninvasive test to assess the colon through use of X-rays; and double contrast barium enema, in which X-rays are taken after a liquid containing barium is put into the rectum. Newer screening tests, called fecal DNA testing, continue to be under study. These tests look for early genetic changes in the colon cells that are sloughed off into the stool.

Once cancer is suspected, further tests will be done to arrive at a diagnosis. These tests may include a computed tomography (CT) scan, double-contrast barium enema X-ray series, and colonoscopy. The CT scan and contrast X-rays reveal abnormal growths, and colonoscopy is similar to sigmoidoscopy but uses a longer, flexible tube in order to inspect the entire colon. During sigmoidoscopy and colonoscopy, the physician can remove polyps and obtain tissue samples for biopsy. A tissue sample is necessary to make the diagnosis of CRC. Microscopic examination of the tissue samples by a pathologist can determine the stage or extent of growth of the cancer. This is important because it helps with assessing the type of treatment needed. In one type of staging, the following criteria are used: stage 0 (cancer confined to epithelium lining of the bowel), stage 1 (cancer confined to the bowel wall), stage 2 (cancer penetrating through all layers of the bowel wall and possibly invading adjacent tissues), stage 3 (cancer invading lymph nodes and/or adjacent tissues), and stage 4 (cancer spreading to distant sites, forming metastases).

The presence of a malignant tumor in the colon requires some form of treatment or a combination of treatments, usually beginning with its surgical removal and followed by radiation therapy and/or chemotherapy (the use of anticancer drugs).

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Surgery is the primary treatment for colorectal cancer. Very small tumors in stage 0 can be removed surgically with the colonoscope. Tumors in more advanced stages require abdominal surgery in which the tumor is removed along with a portion of the bowel and possibly some lymph nodes. For cases in which the bowel cannot be reconnected, an opening is created through the abdominal wall (colostomy). This is usually a temporary procedure, and the hole will be closed when the bowel can be rejoined. Some advanced cancers cannot be cured by surgery alone. Adjuvant therapies-chemotherapy, radiation therapy, and biological therapy-may be used in combination with surgery. Chemotherapy drugs kill spreading cancer cells. The most common is 5-fluorouracil (5-FU), a chemical that interferes with the production of deoxyribonucleic acid (DNA) in dividing cells. 5-FU is more effective when given together with leucovorin (a compound similar to folic acid) and levamisole (an immune system stimulant).

In 2004, the Food and Drug Administration (FDA) approved the use of the Eloxatin injection in combination with 5-FU and leucovorin for the treatment of patients whose cancer has recurred or become worse following initial drug therapy. This approach was shown to shrink tumors in some patients and delay resumed tumor growth. Levamisole and other treatments that reinforce the immune system are forms of biological therapy. Radiation therapy, given either before or after surgery, is helpful in killing undetected cancer cells near the site of the tumor.

PERSPECTIVE AND PROSPECTS

More than 608,000 people worldwide die of colorectal cancer each year, or roughly 8 percent of all cancer deaths. The incidence of colorectal cancer is lower among women than men and rises dramatically after the age of fifty. Colorectal cancer is more common in developed countries and in densely populated, industrialized regions. Populations moving from low-risk parts of the world for developing colorectal cancer, such as Asia or Africa, to high-risk areas, such as the United States or Europe, take on the higher risk within a generation or two, and vice versa.

Research is ongoing to determine the risk factors of colorectal cancers. Recent epidemiological evidence has supported the use of nonsteroidal anti-inflammatory drugs (NSAIDs) as a means of reducing the risk of cancers of the colon and rectum, as well as the risk of intestinal cancers resulting from exposure to carcinogens. The studies focused only on the daily use of aspirin, but similar results have been reported following long-term use of sulindac and indomethacin. Sulindac and celecoxib have shown an ability to induce regression of colon polyps in patients with familial adenomatous polyposis. Researchers are still working on finding the right balance in dose and frequency since NSAIDs have potentially severe side effects and aspirin may induce bleeding if high doses are maintained on a daily basis. Regular cardiovascular exercise and a healthy diet high in fruits and vegetables have also been shown to reduce the risk of developing colorectal cancer.

See also: Biopsy; Cancer; Chemotherapy; Colon; Colon therapy; Colonoscopy and sigmoidoscopy; Colorectal polyp removal; Colorectal surgery; Ileostomy and colostomy; Intestinal disorders; Intestines; Malignancy and metastasis; National Cancer Institute (NCI); Oncology; Radiation therapy; Rectum; Stomach, intestinal, and pancreatic cancers; Tumor removal; Tumors.

For Further Information:

1 

Adrouny, Richard. Understanding ColonCancer. Jackson: University Press of Mississippi, 2002.

2 

Bub, David S., et al. One Hundred Questions and Answers About Colorectal Cancer. 2d ed. Sudbury, Mass.: Jones and Bartlett, 2008.

3 

De Vita, Vincent T., Jr.., Samuel Hellman, and Steven A. Rosenberg, eds. Cancer: Principles and Practice of Oncology. 9th ed. Philadelphia: Lippincott Williams & Wilkins, 2011.

4 

Dollinger, Malin, et al. Everyone’s Guide to CancerTherapy. 5th ed. Kansas City, Mo.: Andrews McMeel, 2008.

5 

Eyre, Harmon J., Dianne Partie Lange, and Lois B. Morris. Informed Decisions: The Complete Book of CancerDiagnosis, Treatment, and Recovery. 2d ed. Atlanta: American Cancer Society, 2002.

6 

Goldman, Lee, and Dennis Ausiello, eds. Cecil Textbook of Medicine. 23d ed. Philadelphia: Saunders/Elsevier, 2007.

7 

LaRusso, Laurie. “Colon Cancer.” Health Library, February 28, 2013.

8 

Levin, Bernard, et al., eds. American CancerSociety’s Complete Guide to Colorectal Cancer. Atlanta: American Cancer Society, 2006.

9 

Miskovitz, Paul, and Marian Betancourt. What to Do If You Get ColonCancer: A Specialist Helps You Take Charge and Make Informed Choices. New York: Wiley, 1997.

10 

Parker, James N., and Philip M. Parker, eds. The Official Patient’s Sourcebook on ColonCancer. San Diego, Calif.: Icon Health, 2002.

11 

“What Is Colorectal Cancer?” American CancerSociety, January 17, 2013.

Citation Types

Type
Format
MLA 9th
Mowbray, Rodney C. "Colorectal Cancer." Magill’s Medical Guide, 9th Edition, edited by Anubhav Agarwal,, Salem Press, 2022. Salem Online, online.salempress.com/articleDetails.do?articleName=MMG2022_0299.
APA 7th
Mowbray, R. C. (2022). Colorectal cancer. In A. Agarwal, (Ed.), Magill’s Medical Guide, 9th Edition. Salem Press. online.salempress.com.
CMOS 17th
Mowbray, Rodney C. "Colorectal Cancer." Edited by Anubhav Agarwal,. Magill’s Medical Guide, 9th Edition. Hackensack: Salem Press, 2022. Accessed September 16, 2025. online.salempress.com.