Better early detection of colon cancer

Dr. Andrea Bannert has been with since 2013. The doctor of biology and medicine editor initially carried out research in microbiology and is the team's expert on the tiny things: bacteria, viruses, molecules and genes. She also works as a freelancer for Bayerischer Rundfunk and various science magazines and writes fantasy novels and children's stories.

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The early detection of colorectal cancer will be even easier from this year: On January 1st, a new guideline of the Federal Joint Committee for the early detection of colorectal cancer came into force. She recommends an immunological test that uses special antibodies to detect blood in the stool more reliably than the previous chemical method.

Most intestinal tumors and their precursors have a sensitive surface with numerous very sensitive blood vessels. In contrast to the healthy intestinal mucosa, they bleed easily. The fine traces of blood in the stool cannot be seen with the naked eye. One also speaks of occult (hidden) blood. So far, this can be proven with a simple so-called guaiac test. If this enzyme-based test is positive, the doctor will then use a colonoscopy to check whether colon cancer is actually the cause of the bleeding.

Eating meat also triggers an alarm

The problem: the guaiac test cannot differentiate between human and animal blood. So anyone who enjoyed a medium steak the night before may produce a positive test result as well as a patient with a tumor in the gastrointestinal tract.

In addition, certain vegetables such as cauliflower, radish, tomatoes or broccoli can interfere with the chemical reaction because the peroxidases they contain trigger the same chemical reaction as hemoglobin. Vitamin C, on the other hand, can inhibit the color conversion, i.e. conceal tumor bleeding.

Specific antibody against hemoglobin

New methods work differently: With the help of specific antibodies, they only detect human blood. A specific protein fits like a key in a lock to the red blood pigment hemoglobin. Such immunological methods are more sensitive and often recognize possible preliminary stages of intestinal tumors, so-called polyps. On average, every fourth of these less than one centimeter large growths on the intestinal wall can be detected in this way. With the old, guajak-based test, it was only about one in ten.

Even if intestinal tumors have already developed, antibody tests are much more sensitive: 60 to 90 percent of all carcinomas are detected in this way - previously it was only 20 to 40 percent.

However, a colonoscopy cannot replace the new antibody screening tests either. Because if the result is positive, it is always the next step. And also the most accurate method: 95 percent of colon tumors are detected with a colonoscopy.

Silent danger

Colon cancer is a malignant growth of the colon or rectum. It develops very slowly and causes hardly any symptoms at first, which is why it is often discovered late. It often arises from degenerate polyps. These initially benign growths can most reliably be recognized by a colonoscopy and removed in the same session.

Sources:

Guideline of the Federal Joint Committee on the Early Detection of Cancer Diseases (Cancer Early Detection Directive / KFE-RL)

Brenner H. et al .: Superior diagnostic performance of faecal immunochemical tests for hemoglobin in a head-to-head comparison with guaiac based faecal occult blood test among 2235 participants of screening colonoscopy, European Journal of Cancer, September 2013.

Cancer information service: Colon cancer - early detection with stool test and colonoscopy, German Cancer Research Center, Heidelberg, accessed: 02.01.2017.

Felix Burda Foundation: Test procedures for colorectal cancer screening in comparison, March 2012.

McLoughlin, R.M., Morain, C.A.O. Colorectal cancer screening. In: World journal of gastroenterology. Volume 12, Number 42, Nov. 2006, pp. 6747-6750.

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