Home > Health A – Z > Colon Cancer

Colon Cancer

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 (680)

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.

Workload and surgeon´s speciality for outcome after colorectal cancer surgery

There is some evidence to suggest better patient outcomes with increasing healthcare provider volume in complex cancer surgery. At present, healthcare providers are unsure of this relationship for colorectal cancer patients and there are mixed views on the concentration of such services to higher volume institutions. Some of the consequences of service centralization would include the loss of local healthcare provision for some patients, and the threat to financial viability of smaller hospitals often relying on a regular income from such a common condition. After thorough search of the available literature, we found fifty‐four observational studies (fifty one meta‐analysed) including 943,728 patients that addressed either the volume‐outcome relationship in the context of modern colorectal cancer treatment, or the effects of surgeon specialization. The results confirm the presence of a volume‐outcome relationship in colorectal cancer surgery, based on hospital and surgeon caseload, and benefits for specialization. For death within five years of treatment, hospital volume appeared to be more beneficial in rectal cancer surgery than for colon cancer. However, international differences in the data suggest provider variability at the hospital level between the different countries, making it imperative that every country or healthcare system must establish audit systems to guide changes in the service provision based on local data, and facilitate centralization of services as required. Overall quality of the evidence was low as all included studies were observational by design. In addition there were discrepancies in the definitions of caseload and colorectal specialist. However ethical challenges associated with the conception of randomised controlled trials addressing the volume outcome relationship makes this the best available evidence.

See all (106)

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

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...