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A new technique to analyze DNA shows that a group of patients do have an inherited form of colon cancer, reports a study conducted at Radboudumc. Routine DNA analysis techniques were not able to determine this previously. Making the correct diagnosis improves treatment and monitoring of patients. Furthermore, their family members can be specifically tested to determine whether they have an increased risk to develop this form of cancer.
With 13,000 new cases per year in the Netherlands, colorectal cancer is one of the most common cancers. Five percent of all colon cancers are hereditary. Most of these are known as Lynch syndrome, caused by abnormalities in four genes in the DNA. These abnormalities are detected by regular analytical techniques. Research leader Richarda de Voer of the Department of Human Genetics at Radboudumc says, ‘In a small group of patients, however, we do not find these DNA abnormalities, even though they are young and have family members with the same type of cancer. These patients seem to have Lynch syndrome, but we could not make the diagnosis. We call this Lynch-like syndrome.'
Waiting eighteen years for a diagnosis
The research team used a new analysis technique on DNA from 32 patients with Lynch-like syndrome. This technique allows to explore regions of the DNA that were previously difficult to analyze. It is the first time it has been used to detect rare hereditary cancers. 'We examine long fragments of DNA with this, whereas previously we could only measure small pieces,' says de Voer. 'Thereby, we explore parts of the DNA that we could not investigate before. Using this technique, we found new abnormalities in two of the four genes involved in Lynch syndrome in six patients. Some patients had been waiting 18 years for a diagnosis, which we can now give them. They have Lynch syndrome.’
Eligible for specific treatment
Being diagnosed with Lynch syndrome improves care for these patients. For instance, there are specific treatments that are very effective for this type of cancer, such as immunotherapy. Patients with Lynch syndrome also have an increased risk to develop other cancers, especially endometrial cancer in women. De Voer: ‘Because we now know what the patient has, we check them much more often and in a more targeted way. Furthermore, doctors can better inform family members about the risks and test for these newly identified DNA abnormalities. They can therefore take away a lot of uncertainty and prevent any unnecessary checkups. Or perform more frequent checkups when there is an increased risk to develop cancer. The researcher sees a bright future for the new technique, which is more widely applicable. 'We are going to detect many more unexplained hereditary cancers with it.'
About the publication
This study was published in Gastroenterology: Noncoding Aberrations in Mismatch Repair Genes Underlie a Substantial Part of the Missing Heritability in Lynch Syndrome. I.B.A.W. Te Paske, A.R. Mensenkamp, K. Neveling, ERN-GENTURIS Lynch-Like Working Group, N. Hoogerbrugge, M.J.L. Ligtenberg, R.M. de Voer. DOI: 10.1053/j.gastro.2022.08.041.
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