Blood tests: Tracking down cancer with circulating DNA

Liquid biopsies in the form of blood tests offer the possibility of analyzing circulating free DNA in the blood and thus improving cancer therapies. The advantage of diagnostics using blood tests is that they can help to detect tumors at an early stage and efficiently monitor the progression of cancer.

In an interview with MEDICA-tradefair.com, Dr. Zsolt Balázs explains in detail the advantages of using blood tests as liquid biopsies compared to imaging procedures and tissue biopsies.

Dr. Balázs, what are the advantages of the new method for analyzing circulating DNA in blood compared to conventional imaging techniques and tissue biopsies?

Dr. Zsolt Balázs: Liquid biopsy has many similarities to tissue biopsy. By this I mean that in both approaches material derived from tumors, such as DNA, RNA or proteins, can be obtained. The key advantage is that liquid biopsies are non-invasive and only blood or other body fluids are taken. In contrast, tissue biopsies often have to be taken surgically. This is associated with the risk of inflammation, which can be avoided with a liquid biopsy.

Imaging procedures provide us with different information. Imaging procedures are more sensitive, but also more expensive. In contrast to CTs and positron emission tomography (PET), however, liquid biopsies have the advantage that patients are not exposed to radiation. For these reasons, liquid biopsies can also be repeated more frequently, which makes it possible to detect tumors more quickly.

What technological advances were necessary to make the sequencing and analysis of circulating free DNA precise and efficient?

Balázs: I think the most important thing was that we already knew exactly what we were looking for. Thanks to basic research over the last ten to 20 years, we have already learned a lot about circulating free DNA, or cfDNA. It started with cfDNA research during pregnancy, where it was discovered that chromosomal changes in the child can be detected in the mother's blood. Today, cfDNA is routinely used in prenatal diagnostics. Through all this previous research, we have found that circulating free DNA from tumors can also be detected.

What's more, the cost of sequencing has fallen sharply since then. And my field, bioinformatics, was still in its infancy at the time. In summary, these three advances were necessary to make the current method possible.

Does the quality of the blood samples affect the reliability and accuracy of the analysis of circulating DNA fragments?

Balázs: A blood sample taken with conventional potassium measuring tubes is perfectly adequate. These samples must be processed quickly after collection, otherwise the blood cells burst and their DNA dilutes the cfDNA. However, the samples can be stored at room temperature for a week in the blood collection tubes specially designed for cfDNA. The test is therefore robust and does not affect the quality of the analysis.

How could the data obtained from the liquid biopsy be implemented in specific personalized treatment plans?

Balázs: One example of its use, as analyzed in our studies, would be in the aftercare of cancer patients who have been treated with radiotherapy. In radiotherapy, it is routine to perform a CT scan immediately after radiotherapy and approximately six months later. During the six months in between, we are blind, so to speak. We don't know whether the tumor has shrunk or continued to grow. The patients are physically examined during this time and blood tests are carried out, but we only find out specific information about the tumors when the next imaging procedure is carried out. In our study, we carried out blood tests during radiotherapy and every three weeks after radiotherapy. This enabled us to detect possible relapses more quickly through the liquid biopsies.

What role could the blood test play in the prevention and early detection of cancer outside of aftercare and therapy monitoring?

Balázs: The blood test has great potential for use in early detection. Early detection of cancer is more difficult than follow-up care. This is because the amount of DNA fragments originating from cancer is smaller and therefore more difficult to find. Nevertheless, early detection has the potential to save more lives and improve patients' quality of life.