Genetic Bowel Cancer
Genetic Bowel Cancer, Colorectal cancer is one of the most common cancers in Germany. In most cases, the cause is unclear. Three to five percent of all cases can be attributed to known gene changes that can be inherited and especially cause colon cancer. Those affected have a very high risk of getting already young. However, there are effective screening programs.
According to data from the Center for Cancer Registry Data at the Robert Koch Institute (RKI), between 62,000 and 64,000 people a year in Germany develop cancer of the colon and rectum. In addition, there are several thousand cases in which early cancer stages are detected. (1) The age focus is clearly in advanced age. More than half of those affected are over 70 years old at the time of diagnosis, and only one in ten are younger than 55. (1)
Often discovered too late
However, this does not apply to people who are affected by hereditary colorectal cancer. They have certain mutations in individual genes that have important functions in the control of the cell cycle and the repair of DNA damage. These genetic defects are passed on via the germ line and cause the disease to undergo diseased remodeling processes in the tissue at an early stage, and those affected usually develop colorectal cancer at unusually young age – between the ages of 20 and 40, for example. (2,3)
Since screening programs such as blood tests in the stool or colonoscopy are offered as standard only from the age of 50 or 55, they are usually too late for these patients. It is all the more important to pay attention to criteria that may indicate the presence of a hereditary colorectal cancer.
How do I recognize my risk?
For a personal danger speaks if close relatives already had colon cancer and the disease occurred at least in one case early (before the 50th year of life). Even if a family member suffers several times in the course of life in the colorectal cancer or in the family more cancers, for example, stomach cancer , uterine cancer or a brain tumor, this may indicate a hereditary tumor syndrome, says Prof. Stefan Aretz, senior physician and specialist in human genetics at the Center for Familial Colorectal Cancer and spokesman for the Center for Hereditary Tumor Diseases at the University Hospital Bonn. A gene change in the germline can affect all body cells, which is why in affected families always cancer in other organs are possible. (2,4)
HNPCC and FAP are the most common forms
Depending on which particular gene mutation is present in a family, different hereditary forms of colon cancer or even tumor syndromes. Basically, a distinction can be made between forms of hereditary colon cancer without polyposis (hereditary non-polypous colorectal carcinoma , abbreviated HNPCC or Lynch syndrome) and hereditary polyposis syndromes.
“Almost all forms of colon cancer, including HNPCC, develop on the basis of polyps, ie benign intestinal tumors,” says Aretz. However, polyposis syndromes are associated with the appearance of uncommonly many polyps in the intestine. In the most common form, the classic familial adenomatous polyposis (FAP), which is also the second most common form of bowel cancer behind HNPCC, affected people usually develop polyps as early as in their teens; later, hundreds to thousands can occur. (5) Hereditary colon cancer without polyposis (HNPCC) does not significantly increase the number of intestinal polyps. According to Aretz, however, this gene mutation shortens the period of carcinogenesis from polyps.
Consequently, people with such genetic defects have a very high risk of developing colon cancer as well as other tumors during their lifetime. According to recent surveys, up to 70 percent of those affected develop colorectal cancer, up to 50 percent of uterine cancer , up to eight percent of ovarian cancer and up to five percent of gastric cancer , without preventive measures . (6) Up to 2% of HNPCC sufferers get CNS tumors (tumors of the brain and spinal cord). (5, 6) Carriers of the FAP mutation have a nearly 100% risk of colon cancer. In other words, without adequate prevention and therapy, they almost always develop colon cancer. (5,7)
Every second child of affected parents inherits the gene mutation
The predisposition for a hereditary tumor disease is passed on to the offspring in most known syndromes with 50 percent probability. Statistically, therefore, every second child inherits the risky inheritance from the affected parent. (8,9)
Definitely let clarify
If there is a suspicion, in any case, a human genetic clarification and advice in a qualified center should be made, stresses Aretz. The specialists there examine the risk of the existence of a hereditary cancer and clarify the further investigations, such as possible genetic tests, and their consequences. The counseling also includes a risk assessment for additional persons in the family. (8, 9, 10) Corresponding contacts to the centers are listed in the service section below.
If the specific familial gene mutation is known through tests on a family member who is already affected, a predictive (predictive) genetic test can be offered to relatives. According to the Genetic Diagnostics Act, such a predictive test should always be carried out as part of human genetic counseling. (4, 8,10)
Genetic testing in many cases allows the safe detection or exclusion of the mutation in a person at risk of the affected family. Ancillary carriers can be detected early and then have the opportunity to take special, close-meshed precautionary measures. (10) “Above all, we also test to relieve those who are not carriers of investment. It does not make sense to send a child for a whole teenage years to colonoscopy, which is not even investment vehicle, “Aretz clarifies. However, in colorectal cancers, such as HNPCC, that are more likely to occur in adulthood, predictive genetic testing is usually not performed until the patient is at least 18 years old and wants a test. Genetic consultations and tests are always voluntary. Patients should be aware in advance
Also, genetic testing does not always bring clarity. Because in some of the inherited bowel cancer, the genetic basis is not or insufficiently researched. If the familial colorectal cancer risk can not be clarified by genetic testing, the diagnosis is made on the basis of the family history and the specifically occurring cancers (the so-called “tumor spectrum”). (5) It is estimated, however, that a large proportion of hereditary cancers are currently not recognized throughout Germany, which means that many people at risk do not receive adequate care. (8th)
Risk persons can provide effectively
Anyone with a family-related increased risk of colon cancer should take precautionary measures. The central element of the prevention is the annual colonoscopy (colonoscopy). It makes it possible to detect mucosal proliferation early and to remove it preventively. For some types of polyposis, such as the classic FAP, annual colonoscopy is recommended as early as the age of 10 to 12, and for HNPCC from the age of 25. (7,11) The chances of preventing the occurrence of malignant tumors through early-onset prevention programs are high, says Aretz.