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Colon and rectal cancers

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of colorectal cancer.

Alternative Names

Colorectal cancer

Staging

A diagnosis of cancer will lead to staging and other tests to help determine the outlook and the appropriate treatments.

Staging

Unlike many other cancers, the size of the tumor is not a major factor in determining the outcome of colorectal cancer. Of greater importance is how far the cancer has spread. To determine this, doctors will assign a stage to the tumor. There are several methods for staging. The older system, known as Dukes', categorizes four basic stages: A, B, C, and D. A more recent system refers to these stages as I, II, III, and IV but divides the categories slightly differently. The term "5-year survival" means that patients have lived at least 5 years since diagnosis. Most patients who live 5 years without a recurrence are considered to be cured of their disease.

Stage	Condition	5-Year Survival
A or I	Tumor superficially involves the inner lining of the intestine.	More than 90%
B or II	Tumor has penetrated through the muscle wall of the intestine but has not reached the lymph nodes.	70 - 85%
C or III	Lymph nodes are involved.	65% or below
D or IV	Tumor has spread to other organs (metastasized), usually the liver first.	5 - 9%

Tumor Markers

Researchers are continually seeking to identify tumor markers, substances (usually found in blood samples) that will assist in the diagnosis of cancer and in monitoring effects of treatment.

Carcinoembryonic Antigen (CEA). High blood levels of a protein called carcinoembryonic antigen (CEA) sometimes indicate the presence of colon cancer. Unfortunately, it is also elevated in other cancers and in some noncancerous conditions. CEA is not effective as a screening tool for healthy people, but might eventually be helpful for patients with cancer.

• An advanced diagnostic technique called polymerase chain reaction (PCR) can detect genetic evidence of CEA. One study indicated that when these microscopic footprints of colon cancer are detected in the lymph nodes of Stage II patients (whose lymph nodes otherwise appear to be not involved with cancer), the outlook is similar to that of Stage III patients. Patients without this so-called micrometastasis have a very favorable prognosis. Further research is needed, however, before PCR can be used in widespread practice.
• In patients with a history of, or active, colon cancer, follow-up measuring of blood CEA levels may be helpful in detecting recurrence of the cancer and effectiveness of treatments.

Defective P53 Gene. The presence of a defective p53 gene is a marker for very poor prognosis in patients with advanced colon cancer. In its normal state, the gene is important for regulation of cell growth. Testing for this abnormality, however, is not widely done because it is not clear how to use this information.

Other Tumor Markers. Other tumor markers under investigation include a protein called GLUT1, cancer antigen 19-9 (CA 19-9), matrix metalloproteinase-9 (MMP-9) RNA, HER-2/neu oncoprotein, transforming growth factor beta-1 (TGF-beta-1), and CD44.

Sentinel Node Biopsy

A technique known as a sentinel node biopsy is increasingly performed by experienced surgeons in selected patients. This procedure is used to determine if cancer has spread beyond the nodes, possibly reducing the need for complete axillary lymphadenectomies. It involves the following:

• The procedure uses an injection of a tiny amount of a tracer, either a radioactively-labeled substance (radioisotope) or a blue dye, into the tumor site.
• The tracer or dye then flows via the lymphatic system into the so-called sentinel node . This is the first lymph node to which any cancer would spread.
• The sentinel lymph node and possibly one or two others are then removed.
• If they do not show any signs of cancer, it is highly likely that the remainder of the lymph nodes will be cancer free, and further surgery becomes unnecessary.

It is still not known if the sentinel node biopsy has any survival advantages compared to the standard procedures with lymph nodes removal. However, a 2002 study indicated that careful and complete removal of potentially cancerous lymph nodes is still very important for improving survival in Stage II and III patients.

• Review Date: 3/6/2007
• Reviewed By: A.D.A.M. Editorial Team: Greg Juhn, M.T.P.W., David R. Eltz, Kelli A. Stacy. Previously reviewed by Harvey Simon, M.D., Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital (9/1/2006).

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