When a brain tumor has been removed from patients, there is a high chance that the tumor will come back. That is why they have a follow-up check with an MRI scan every three months. The researchers, led by Florent Moulière, based in Amsterdam UMC, and Richard Mair of the Cancer Research UK Cambridge Institute, University of Cambridge, developed two different methods of doing this. Moulière: “Although this research is still in its early stages and only a small number of patients have been analysed, the results are promising. In the future, this may lead to the patient having a regular urine test at home instead of an MRI scan. The test could detect a recurrent cancer earlier and more easily.” Mair continues, “This can also help physicians determine next treatment steps and improve patient outcomes.”
Blood tests for detecting cancer are mainly based on finding tiny amounts of DNA that are released when tumor cells die. This DNA is known as cell-free DNA and is measurable in body fluids such as urine and plasma. However, measuring brain tumor cell-free DNA in the blood is difficult because of the blood-brain barrier. This is a virtually impenetrable line between the brain and the bloodstream. As a result, the cell-free DNA can only be found in blood in very low concentrations. But the team of researchers was not deterred by this challenge. They are the first to detect brain tumors by measuring DNA from these tumors using a urine test.
Mutations in the tumor DNA
As the first way to detect brain tumors, the researchers look at the DNA of a piece of the patient’s brain tumor tissue. This DNA contains unique mutations, which they then try to detect in the patient’s urine, blood or plasma. “We analyze the tumor’s DNA after a tissue biopsy to identify as many mutations as possible. We then try to track these mutations in different bio-fluids from the same patient,” says Moulière. “The big advantage is that this method allows us to focus on the mutations that were originally present in the tumor, thereby improving treatment outcomes.”
Length of the tumor DNA
For the second approach, the researchers looked for other patterns in the cell-free DNA that could also indicate the presence of a tumor, without having to identify the mutations. They analyzed 35 samples from glioma patients, 27 people with non-cancerous brain disorders and 26 healthy people. They found that fragments of cell-free DNA from patients with brain tumors were of a different length than those from patients without tumors. They then fed this data into a machine learning algorithm that was able to successfully differentiate between the urine samples from people with and without glioma.
Less invasive and cheaper
Both tests are less expensive than an MRI and can be taken outside the hospital or even at home, and more often. “It is also more pleasant for the mental health of the patient not to have to go to the hospital and have to undergo an MRI scan,” says Moulière.
The next steps are to use the urine test in a trial of patients with brain tumors who are in remission. The researchers want to know whether the regular urine test can determine that the tumor comes back at the same time or earlier than the control MRI.
Detecting brain tumors with a simple urine test
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