By: Dr. Irit Chermesh, Specialist in Internal Medicine and Gastroenterology, Rambam Medical Center

Colon cancer is very common, and is the second most common cause of mortality from malignant diseases in the US and Europe. It is more frequently diagnosed among people over the age of 50 (both men and women), but the disease can also strike young people, and even adolescents.
Life expectancy following diagnosis of colon cancer is directly linked to the stage at which the disease was diagnosed. If the disease is diagnosed at an early stage, the chance of cure is 90%. However, if diagnosis is performed at an advanced, metastatic stage, the chance of cure is very low, less than 5%.
In most cases, colon cancer develops from a benign lesion formed in the mucous tissue lining the colon. This lesion is called “adenoma”. The transition from adenoma to cancer is a long process, usually lasting several years. Therefore, early detection and excision of the adenoma can usually prevent the development of a cancerous tumor.

There are several diagnostic methods for early detection and prevention of colon cancer. None of these methods is ideal, as each of them has advantages and disadvantages. However, it is now clear and it has been proven that undergoing these tests is of great importance. Early diagnosis and treatment of the disease can affect morbidity, as well as mortality, and can prevent, in some cases, the need for operations involving abdominal opening.

Types of tests available:

Fecal occult blood test
Malignant and pre-malignant lesions in the gastrointestinal tract tend to bleed. Therefore, detection of fecal blood indicates the existence of an abnormal process, and requires further evaluation.
For people of 40 years of age and older, it is recommended to perform the test on two samples, from three consecutive stools (a total of 6 tests), once a year.

Sigmoidoscopy

Endoscopic test of the gastrointestinal tract, into which a camera connected to a flexible tube is inserted, enabling the direct observation by the physician by means of a television screen. The test is limited to the rectum and the sigmoid.
Recommended as a supplementary test, in addition to the fecal occult blood test, for men and women of 50 years of age and older, once every 5 years.

Colonoscopy

The most accurate test, enabling observation of the entire large intestine. A tiny camera on a flexible tube (endoscope) is inserted through the anus. In parallel, the colon is inflated with air for optimal observation. The colonoscopy takes more time than a sigmoidoscopy, and enables the physician to take samples (biopsies) and to remove polyps, if detected.
Recommended once every 10 years for people of 50 years of age and older.

Virtual colonoscopy (CT-based colography)

A test based on a CT scan, based on X-ray imaging and computerized image processing, to produce three dimensional images of the colon in order to look for tumorous processes. During this test, a thin tube is inserted through the anus (via this tube, the colon is inflated with air, which dilates the colon).
The accuracy level of this test is variable and depends on the size of the polyps. Interpretation of the test results is directly dependent on the experience of the interpreter, leading to numerous discrepancies between different interpretations. In addition, the test is associated with a considerable amount of radiation, and there are also cases of perforation following the exam, although these are very rare.

Barium enema

A series of X-rays, performed after introducing a contrast medium named barium, which is visible on X-ray images. The barium is introduced through the anus by enema. Abnormalities in the intestine will be visible on the X-ray image. The test is highly accurate and is used mainly after failure in performing a colonoscopy and in places where colonoscopy is not available.
Recommended once every 5 years for people of 50 years of age and older.