A blood test could detect 50 different types of cancer. The studies for its development were funded by the company GRAIL, Inc. of California, United States. The firm assures that this analysis not only detects if a person has cancer but where it is located in the body.
The results of the study were published in the journal Annals of Oncology in late June. Scientists around the world have investigated the optimization of these methods and there are already several encouraging approaches. “But despite the first promising results, further research is needed before a reliable cancer screening test is available for widespread use in the population,” warns Susanne Weg-Remers of the Cancer Information Service at DKFZ, the German Cancer Research Centre in Heidelberg.
Weg-Remers remains skeptical following the trumpeted announcement of the cancer screening. “In order for cancer to be early detection through a blood test, it is necessary to carry out other clinical studies with a very large number of people. Only then can we be sure that those who use this test really benefit from it, that is to say that cancer is detected reliably, accurately and so early that there is a good chance of cure. Any potential risks from the test must be kept within the limits,” he says.
Recognition of matrix cancer through magnetic resonance imaging
Analysis with the help of artificial intelligence
Several prerequisites are necessary for a blood test to detect cancer. Cancer cells, parts of their DNA, or typical cancer biomarkers must circulate through the bloodstream. Only then can the blood test detect the tumor. “The blood test presented in California examines the genetic information released into the blood by potential tumor cells. Methylation patterns are obviously altered when there is a specific tumor in the body,” explains Weg-Remers. These methylation patterns are different in degenerated cells, that is, in cancer cells.
The new U.S. blood test is supposed to be able to determine more than a million sites of a DNA, an algorithm evaluates the results and assigns the patterns to different types of cancer and tissues. In the latest California partial study, researchers examined 2,823 people who had already been diagnosed with cancer and 1,254 healthy people. The more advanced the cancer was, the more often there was a result.
“To characterize the right tests for early detection, sensitivity is critical. That is, you have to see how often the test correctly detects a tumor, and you also have to determine the specificity, that is, how often the test correctly detects that there is no tumor. These are two important parameters for a test that you want to use for early detection,” explains Weg-Remers. Especially in the early stages of the disease, tumors often go unnoticed because there are often no symptoms yet.
But there are other pitfalls: in some people, tests indicate a tumor even if it doesn’t exist. Therefore, the result is a false positive. But there are also false-negative results when an existing cancer is not detected by the test. The patient feels safe, but this safety is not only misleading, but can become deadly if the cancer is not treated.
Blood tests: fear as a business
In Germany, there is currently no blood test for the early detection of cancer whose benefit has been positively assessed and which is therefore covered by health insurance. The same PSA for the early detection of prostate cancer remains controversial.
There are not always purely medical reasons to drive research, Weg-Remers warns, adding, “There are companies that have developed the fear of cancer with blood tests as a business model, so to speak. They offer these tests on a self-payer. Then, the patient undergoes such a test, gets an unremarkable result and is neglected with a deceptive sense of security, or he gets very scared and undergoes more tests because the test has supposedly found a tumor.”
