Home > Health A – Z > Colon Cancer

Colon Cancer (Colon Carcinoma)

Cancer that forms in the tissues of the colon (the longest part of the large intestine).

PubMed Health Glossary
(Source: NIH - National Cancer Institute)

About Colon Cancer

Colon cancer is a disease in which malignant (cancer) cells form in the tissues of the colon.

The colon is part of the body's digestive system. The digestive system removes and processes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) from foods and helps pass waste material out of the body. The digestive system is made up of the esophagus, stomach, and the small and large intestines. The first 6 feet of the large intestine are called the large bowel or colon. The last 6 inches are the rectum and the anal canal. The anal canal ends at the anus (the opening of the large intestine to the outside of the body).

Gastrointestinal stromal tumors can occur in the colon. See the PDQ summary on Gastrointestinal Stromal Tumors Treatment for more information... Read more about Colon Cancer

What works? Research summarized

Evidence reviews

Venous Thromboembolism: Reducing the Risk of Venous Thromboembolism (Deep Vein Thrombosis and Pulmonary Embolism) in Patients Admitted to Hospital

Venous thromboembolism (VTE) is a term used to include the formation of a blood clot (a thrombus) in a vein which may dislodge from its site of origin to travel in the blood, a phenomenon called embolism. A thrombus most commonly occurs in the deep veins of the legs; this is called deep vein thrombosis. A dislodged thrombus that travels to the lungs is known as a pulmonary embolism.

Strategies for detecting colon cancer and/or dysplasia in patients with inflammatory bowel disease

Patients with long‐standing ulcerative colitis and colonic Crohn's disease have an increased risk of colorectal cancer compared with the general population. This review shows that there is no conclusive evidence that surveillance colonoscopy prolongs survival in these patients. However, since the principal studies were completed it has become clear that numerous biopsies are needed to accurately identify pre‐cancerous lesions (dysplasia) and that the benefit of surveillance could have been greater if multiple biopsies had been performed. It has also since been demonstrated that targeted biopsy of dysplastic areas is enhanced by dye spraying at colonoscopy. There is evidence from case control studies that cancers tend to be detected at an earlier stage in patients who are undergoing surveillance and that these patients have a better chance for recovery. This evidence should be treated with caution since lead‐time bias (the period between early detection of disease and the time of its usual clinical presentation) may contribute substantially to this apparent benefit. It is unlikely that there will be a randomised trial of surveillance colonoscopy in patients with colitis. Lower quality evidence, however, supports the continued use of some form of surveillance for these patients. The nature of this surveillance is gradually evolving, with two important developments since the last version of this review in 2004. Firstly, it has become apparent that most pre‐malignant (dysplastic) lesions can be visualised with careful endoscopy. Secondly, patients who lack histological inflammation on colonoscopy are at low risk for cancer development.

Adjuvant therapy for completely resected stage II colon cancer

Colon cancer is the second most common cause of cancer deaths in the Western world. A large proportion of colon cancer patients can be cured by surgical resection alone. For those patients with lymph node positive (stage III) disease, the recurrence rate can exceed 50% and adjuvant chemotherapy has been shown to significantly reduce the risk of recurrence. In patients without lymph node involvement (stage I and II), the prognosis is quite good with surgery alone, with survival rates of 75% to 95% at 5 years. However, some patients with high risk stage II disease have a relapse rate approaching that of stage III colon cancer patients. Due to the effectiveness of systemic chemotherapy in stage III disease, a similar approach has been considered for patients with stage II disease. We performed a systematic review looking at all randomized clinical trials evaluating stage II colon cancer patients and adjuvant therapy versus surgery alone. Our review found that adjuvant therapy ‐either systemic or regional chemotherapy or immunotherapy‐ can improve the outcomes of stage II patients. In counselling individual patients, the advice given should be conditioned by the patient's age and comorbidities. In addition, the high risk features of the tumour should also be considered when contemplating the benefits of systemic therapy in patients with stage II colon cancer. Further investigation is needed to elucidate which patient and tumour factors can be used to select stage II colon cancer patients for adjuvant therapy. There also exists a need to continue to search for other adjuvant therapies which might be more effective, shorter in duration and less toxic than those available today.

See all (706)

Summaries for consumers

Strategies for detecting colon cancer and/or dysplasia in patients with inflammatory bowel disease

Patients with long‐standing ulcerative colitis and colonic Crohn's disease have an increased risk of colorectal cancer compared with the general population. This review shows that there is no conclusive evidence that surveillance colonoscopy prolongs survival in these patients. However, since the principal studies were completed it has become clear that numerous biopsies are needed to accurately identify pre‐cancerous lesions (dysplasia) and that the benefit of surveillance could have been greater if multiple biopsies had been performed. It has also since been demonstrated that targeted biopsy of dysplastic areas is enhanced by dye spraying at colonoscopy. There is evidence from case control studies that cancers tend to be detected at an earlier stage in patients who are undergoing surveillance and that these patients have a better chance for recovery. This evidence should be treated with caution since lead‐time bias (the period between early detection of disease and the time of its usual clinical presentation) may contribute substantially to this apparent benefit. It is unlikely that there will be a randomised trial of surveillance colonoscopy in patients with colitis. Lower quality evidence, however, supports the continued use of some form of surveillance for these patients. The nature of this surveillance is gradually evolving, with two important developments since the last version of this review in 2004. Firstly, it has become apparent that most pre‐malignant (dysplastic) lesions can be visualised with careful endoscopy. Secondly, patients who lack histological inflammation on colonoscopy are at low risk for cancer development.

Adjuvant therapy for completely resected stage II colon cancer

Colon cancer is the second most common cause of cancer deaths in the Western world. A large proportion of colon cancer patients can be cured by surgical resection alone. For those patients with lymph node positive (stage III) disease, the recurrence rate can exceed 50% and adjuvant chemotherapy has been shown to significantly reduce the risk of recurrence. In patients without lymph node involvement (stage I and II), the prognosis is quite good with surgery alone, with survival rates of 75% to 95% at 5 years. However, some patients with high risk stage II disease have a relapse rate approaching that of stage III colon cancer patients. Due to the effectiveness of systemic chemotherapy in stage III disease, a similar approach has been considered for patients with stage II disease. We performed a systematic review looking at all randomized clinical trials evaluating stage II colon cancer patients and adjuvant therapy versus surgery alone. Our review found that adjuvant therapy ‐either systemic or regional chemotherapy or immunotherapy‐ can improve the outcomes of stage II patients. In counselling individual patients, the advice given should be conditioned by the patient's age and comorbidities. In addition, the high risk features of the tumour should also be considered when contemplating the benefits of systemic therapy in patients with stage II colon cancer. Further investigation is needed to elucidate which patient and tumour factors can be used to select stage II colon cancer patients for adjuvant therapy. There also exists a need to continue to search for other adjuvant therapies which might be more effective, shorter in duration and less toxic than those available today.

Comparison of two methods used in screening for colorectal cancer

Cancer in the large intestine (colon) and rectum is one of the most frequent cancers in developed countries. The disease develops from benign lesions over a time span of about 10 years. If the lesion has turned into cancer, the prognosis is far better if the disease is detected at an early stage. Screening and detection for early cancers and benign precursors may therefore reduce the number of deaths caused by this disease. Cancers and benign precursors may bleed, and the blood can be detected in the stool by specific tests, the so‐called faecal occult blood tests (FOBT). If the test is positive (that is blood is detected), the person will be offered a colonoscopy to find the source of bleeding. Unfortunately, FOBT fails to discover a considerable number of cancers and precursor lesions. Therefore, endoscopic examination of the rectum and lower large intestine (the sigmoid colon) has been advocated (called flexible sigmoidoscopy). Flexible sigmoidoscopy is performed with a flexible instrument inserted through the anus and introduced about 50 centimetres into the lower large intestine after cleansing with a small enema. This allows direct visual inspection of the interior wall of the intestine, and benign lesions and malignant tumours may be detected. Benign lesions may be removed in the same session without anaesthesia and without any discomfort for the patient, and a follow‐up colonoscopy may be offered.

See all (116)

Terms to know

Colon (Bowel)
The longest part of the large intestine, which is a tube-like organ connected to the small intestine at one end and the anus at the other. The colon removes water and some nutrients and electrolytes from partially digested food. The remaining material, solid waste called stool, moves through the colon to the rectum and leaves the body through the anus.
Gastrointestinal Stromal Tumor (GIST)
A type of tumor that usually begins in cells in the wall of the gastrointestinal tract.
Large Intestine
The part of the intestine that includes the appendix, cecum, colon, and rectum. The large intestine absorbs water from stool and changes it from a liquid to a solid form. The large intestine is 5 feet long.
Rectum
The last several inches of the large intestine closest to the anus.

More about Colon Cancer

Photo of an adult

Also called: Malignant tumour of the colon, Malignant tumor of the colon, Cancer of the colon, Carcinoma of the colon, Colonic carcinoma

Other terms to know: See all 4
Colon (Bowel), Gastrointestinal Stromal Tumor (GIST), Large Intestine

Related articles:
Cancer: Anxiety and Distress
Information for Health Professionals

Keep up with systematic reviews on Colon Cancer:

Create RSS

PubMed Health Blog...

read all...