Stichting Lynch Polyposis (NL)
Hereditary non-polyposis colorectal cancer (HNPCC) or Lynch syndrome is an autosomal dominant genetic condition that has a high risk of colon cancer, as well as other cancers including endometrial (second most common), ovary, stomach, small intestine, hepatobiliary tract, upper urinary tract, brain and skin cancer. The increased risk for these cancers is due to inherited mutations that impair DNA mismatch repair. In colon cancer patients, it is estimated that up to 5% have Lynch syndrome. In endometrial cancer this percentage is between 2 and 5%.
Patients with Lynch syndrome have a 25 to 70% higher chance of contracting colon cancer than people without the syndrome. For endometrial cancer the risk is 15 to 55% higher. For all cancers, Lynch patients run a 1 to 15% higher chance of contracting them.
The exact number of Lynch syndrome patients in Belgium is not known because many people are not aware of having this rare condition.
A doctor may suspect that Lynch syndrome is involved in the following situations:
Mutations in certain genes can lead to the Lynch syndrome. These genes are:
All of these genes play a part in recognising and repairing damaged DNA. Every person has a double set of these genes, one from the paternal and one from the maternal side. The healthy non-mutated gene ensures that the mutations from the other pair are recognised and neutralised, but as a patient grows older the healthy gene also begins to falter so that not all DNA mutations are recognised. This can lead to cancer. A carrier of the Lynch syndrome has a 50% chance of passing the syndrome on to a child, due to the autosomal dominant aspect.
When a doctor suspects the Lynch syndrome might be present in a patient, they can have a biopsy done and have the tumorous tissue tested for mutations in one of the four associated genes. A clinical geneticist can do further tests.
Two test methods are:
People with Lynch syndrome are advised to undergo frequent, often annual, screening. Early diagnosis improves the outlook of patients. Lynch patients who undergo regular testing have the same life expectancy as healthy persons.
Check-ups routinely involve colon examination. These usually start with patients from the age of 25. Commonly these involve colonoscopy, sometimes combined with surgical removal of suspicious polyps. Women between the ages of 40 and 60 are invited to have their uterus and endometrium examined once a year. These tests include:
There is little point in periodically checking Lynch syndrome patients for other cancers, but it is often advised that patients have themselves checked for the presence of Helicobacter Pylori, a bacteria that occurs in the stomach and can be an indicator for an elevated risk of stomach cancer.
Treatment of cancers for a Lynch syndrome patient are no different from the treatment for other people with the same cancers. The only exception involves colon cancer. When a Lynch syndrome patient has developed colon cancer, full removal of the large intestine can be recommended. This will significantly reduce the chance of the cancer returning, and it will also make the annual screening a lot less invasive. In patients over 60, the advice is often to remove just a part of the colon: removing the entire colon in elderly patients does not significantly reduce the chance of the cancer coming back in the same way it does in younger patients. Sometimes the colon, or a part of it, is removed preventively, for instance when polyps frequently occur. Research into PI3K, AKT and mTOR inhibitors is currently ongoing as a potential therapy for eligible patients.
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