Cancer under control
A blood test will help track the progress of cancer treatment
According to the head of the study, the results of which are published by Nature, Carlos Caldas, depending on the degree of the disease, tumor DNA can make up from less than one to 50 percent of extracellular DNA that is present in blood plasma. The authors estimated its number by mutations associated with malignant neoplasms, in particular, by two genes, TP53 and PIK3CA.
The development of the method began with 52 patients, but "iconic" mutations in these two genes were first found in only 25 of them. Genome-wide sequencing made it possible to identify markers for tracking tumor DNA in five more of the remaining patients.
According to Kaldas, "in each type of breast cancer, at least one mutation can be found for monitoring."
Commenting on the publication of colleagues, an oncologist from the University Clinic Hamburg-Eppendorf, Germany, Klaus Pantel, who deals with tumor DNA circulating in the bloodstream, notes both the strengths and weaknesses of the proposed method. "Testing for specific mutations can be very sensitive, but not every tumor has these markers," says the expert.
The authors note that the technique can be adapted to the specifics of individual patients.
Daniel Haber of the Massachusetts General Hospital Cancer Center called the technique of tracking cancer by circulating DNA "powerful." Both he and Pantel believe that this approach is a valuable addition to the growing range of non-invasive biopsy alternatives.
Methods for assessing the progress of anti-cancer therapy by how cells leave the tumor and enter the bloodstream are being developed in many laboratories. And although circulating tumor cells are more difficult to isolate than DNA, as Pantel notes, they carry additional information about the RNA and protein profile of the tumor.
Kaldas and colleagues compared their method with a test for circulating tumor cells called CellSearch. It has been approved by the U.S. Food and Drug Administration (FDA) for predicting advanced forms of breast, colon, rectal, and prostate cancers. The test for circulating tumor DNA turned out to be more sensitive. Nevertheless, as both the authors and experts note, before routine clinical use, the new approach should be replicated in more extensive randomized trials.
Portal "Eternal youth" http://vechnayamolodost.ru15.03.2013