If it turns out to be possible to diagnose cancer at an earlier stage with a blood test, this would be a great advance in the treatment of the disease. The United States has developed just such a test, but its reliability is not indisputable, writes “Deutsche Welle“.
A blood test developed by GRAIL in California can detect 50 types of cancer. Tests show not only the presence of cancer cells, but also their location in the body. The results of the study were published in late June in the specialized publication “Annals of Oncology”.
More research is needed
Susanne Weg-Remers of the German Cancer Research Center in Heidelberg is skeptical about the results of the blood test. “For a blood test to be suitable for early diagnosis, further clinical trials must be performed with a very large number of patients. This is the only way to be sure that those who use this test will actually have benefit from it, ie the cancer will be detected reliably, accurately and at such an early stage that there is a great chance of cure, “says Veg-Remers.
In order for a blood test to identify cancer, different prerequisites must be present. Cancer cells, parts of their DNA or cancer-specific biomarkers need to circulate in the blood. Only then can a blood test detect a tumor.
“The described blood test examines the genetic information that is thought to be separated in the blood from possible tumor cells,” explains the German expert.
The American blood test must be able to recognize over one million pieces of DNA, after which an algorithm evaluates the results and compares them with models of different types of cancer and tissues. The latest partial study in California involved 2,823 people who had already been diagnosed with cancer and 1,254 healthy volunteers.
Early diagnosis is key
“In order to evaluate tests that are suitable for early diagnosis, it is important to first know how sensitive they are. This means seeing how often the test correctly detects a tumor, and determining the frequency with which the test correctly reveals the absence of a tumor, ”says Veg-Remers. Tumors are missed more often in the early stages of the disease, when there are no symptoms yet. “But that’s when it would make sense to use tests that reliably detect cancer.”
The new blood test was able to detect diseases at different stages in more than 50 different types of cancer. On average, 51.5 percent of the results are correctly positive, while 99.5 percent of the test results are correctly negative.
Efficiency at an advanced stage is high
The more advanced the cancer, the higher the recognition rate. Thus, in patients in the advanced fourth stage, it is 90.1 percent. However, the result of early detection is much lower – in the first stage only 16.8 percent were recognized. Or, to put it another way: in about 83 percent of cases, early-stage cancer is not detected by the test.
Veg-Remers warns that not only do wrong results create risks – they can also lead to pre-diagnosis. “Cancer can be found that would not cause problems for the patient. There are tumors that grow so slowly that they never become symptomatic. If such a tumor is detected by a blood test, the patient becomes cancer with the corresponding consequences. And it can be undergoing serious treatment that is not necessary. ” A simple blood test should detect cancer
Germany does not currently pay for blood cancer tests
In Germany, there is still no blood test to detect cancer that is considered effective and is covered by the health insurance fund. In the United States, the early detection test for many cancers is now available by prescription. It serves as a supplement to existing methods for screening for some common cancers and for early detection of cancers for which there are no proven research methods – pancreatic and esophageal cancer, as well as liver cancer.
In any case, there is no reliable test for any type of cancer – many more studies are still needed.
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