A team of scientists from different institutions in the Netherlands, Denmark and the USA, coordinated by researchers from the Johns Hopkins University School of Medicine, in the latter country, has devised a new type of analysis that allows the detection of fragments of Tumor DNA, released by cancer cells, in a blood sample. According to these experts in a study published in the journal Science Translational Medicine , it is a non-invasive strategy with which it is possible to determine whether an individual will develop cancer while still in the initial stages of the disease. In the trial, they remember that the earlier the diagnosis is confirmed, the faster treatment can be started , which improves the chances of overcoming this disease.
Telltale mutations
This technique, called TEC-Seq, optimizes sample preparation and combines sequencing and computational analysis. Thus, it reveals the presence of said DNA and distinguishes it from other genetic material that has undergone alterations and that could be mistakenly taken by a tumor biomarker. With it, they have examined 200 patients suffering from colorectal, breast, lung and ovarian cancer, and have identified with great precision the presence of somatic mutations – these can be the cause of the growth of certain tumors – in the plasma of more than half of them, specifically, in 71%, 59%, 59% and 68% of them, respectively. To do this, they looked for mutations in 58 genes related to the appearance of cancer. In addition, they did not find those that would allow to point to the presence of the disease in the samples of 44 healthy individuals.
“Our work shows that it is feasible to identify cancer early from certain changes in the DNA in the blood , and that to achieve this goal the sequencing system that we have developed is very promising”, indicates Victor Velculescu, professor of Oncology at the Kimmel Cancer Center at Johns Hopkins University and one of the study’s co-authors. “It has been a challenge to devise a technique that allows us to predict the probable existence of cancer without knowing the genetic mutations present,” he says.
False positives
Jillian Phallen, from the same US institution, who has also collaborated in this initiative, emphasizes that it also reduces the risk of false positives, erroneous results that often multiply the number of tests and the implementation of unnecessary treatments. Velculescu gives an example: when blood cells divide they can undergo mutations. In certain cases, these changes may lead to preleukemia, but this is not usually the case.
Despite the good results, the researchers caution that this system will need to be tested in studies with many more people before validating it . In fact, it takes into account more than 80,000 DNA base pairs, which makes it very expensive, although scientists hope to fine-tune it to reduce the costs of the process.
Reference: Jillian Phalen et al. Science Translational Medicine 16 Aug 2017: Vol. 9, Issue 403, eaan2415. DOI: 10.1126 / scitranslmed.aan2415
Image: Ernesto del Aguila III / NHGRI / NIH
