"Liquid biopsy" for early cancer diagnosis
A prototype analysis has been developed to determine cancer from a blood sample
Anna Stavina, XX2 century, based on Medical Xpress: Scientists move closer to detecting cancer long before any symptoms appear
"Liquid biopsy", the analysis of tumor DNA circulating in the blood, is already used in oncology. But for now — only for the selection of optimal treatment options or the detection of relapses.
Scientists around the world are trying to find a way to detect oncological diseases before they become deadly. The work is not yet complete, but judging by the results of a recent study, we are one step closer to solving this puzzle. A special blood test can detect fragments of mutated DNA in the early stages, when the tumor cannot yet be detected by any of the existing devices.
The results of the study were presented at the annual conference of the American Society of Clinical Oncology (American Society of Clinical Oncology). According to the data provided, 73% of the mutations found in the tumors of 124 cancer patients were also found in DNA fragments that moved freely in the bloodstream.
The new diagnostic method was developed by GRAIL, located in San Francisco is the "daughter" of the genetic giant Illumina. To detect mutated fragments, scientists used "high-intensity" sequencing, assuming that the parts of the genome of interest will be read on average 60 thousand. once in order to increase accuracy. GRAIL plans to use the new method in a study that will involve 10,000 Americans — people with cancer and those who do not have a cancer diagnosis.
"The discovery of a direct link between the diagnosed tumors and the fragments of mutated DNA circulating in the bloodstream is an important first step on a long road to creating approaches that will allow using a blood test to determine who has cancer and who does not," said Dr. Mark Lee, head of GRAIL Clinical Development department.
As the name of the company suggests, the development of a blood test that can detect cancer before it appears on X—rays is the Holy Grail of modern cancer prevention. Theoretically, if doctors have the opportunity to detect a tumor early enough and determine how aggressive it is, doctors will be able to prescribe treatment much more effectively, while choosing the optimal drugs and methods from an ever-expanding arsenal of ways to fight cancer. The latest developments in this field belong to the category of immunotherapy, drugs that force the patient's own immune system to destroy tumors or at least restrain their growth.
According to GRAIL experts, the hypersensitive method of cancer detection developed by them generates about 100 times more data than conventional screening studies.
Examination of one patient results in approximately 1 terabyte of data.
In recent years, genome sequencing technologies have advanced far, as well as data processing methods, which led to the emergence of the so-called "liquid biopsy". The fact is that all cells in the process of vital activity release DNA fragments into the surrounding intercellular space. And tumor cells are no exception. But there is one problem — almost all the "extracellular" DNA circulating in the bloodstream has "fallen out" of ordinary healthy cells. The share of "cancer" DNA accounts for only one tenth of a percent. This means that diagnostic tests based on a "liquid biopsy" should be very, very accurate when it comes to detecting specific mutations indicating the presence of cancer.
GRAIL is not the first company to develop tests based on "liquid biopsy". Doctors are already sending blood samples of their patients today so that specialists in the laboratory can study the DNA tumors. These studies help doctors determine which of the targeted drugs is better to prescribe, they also provide information about the stages of the disease and the onset of relapses. However, the very diagnosis of cancer based on a blood test still loomed somewhere on the horizon of the possible.
The fundamental difference between the approach used in GRAIL is that the company uses data from large-scale clinical trials in its work. Only after analyzing thousands and thousands of samples, it is possible to determine what the appearance of a particular tumor-associated DNA fragment in the bloodstream means. Does the patient have a tumor? Will it become a problem and, if so, how soon? The creators of the new test hope that over time their brainchild will be able to give answers to all these questions.
Portal "Eternal youth" http://vechnayamolodost.ru
13.06.2017