“You will probably never get the accuracy of a colonoscopy with tests, for example, but in theory it is much easier to screen numerous cancers with a simple blood test,” says Gunnar Folprecht of the University Cancer Center Dresden. In any case, the initial diagnosis must be confirmed by further, more targeted examinations. Why: Often shows a false positive result. Then the alarm sounds falsely. This could burden patients unnecessarily. “The general problem with these tests is that if the test result is false positive, the affected people are exposed to psychological and physical stress due to the further diagnostics that are then triggered,” says Ulrich Hacker of the University of Cancer Center. Leipzig.
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Uncertainty about whether or not you have cancer can put a strain on your psyche. Further tests to verify the diagnosis can be quite inconvenient. For example, if an endoscopy is done if gastric cancer is suspected. If the diagnosis were wrong, the patient would have nothing to worry about.
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Possibility of overdiagnosis
Overdiagnosis must be clearly distinguished from misdiagnosis. There is already an approved test for the early detection of prostate cancer, which practices usually offer as an “individual health service”. The PSA test examines the proteins produced in the prostate. If there are too many of these proteins in the blood, this can indicate cancer or another prostate disease
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In this way, many cases of prostate cancer are diagnosed which would never have emerged without the test and which would not have caused any symptoms in the patient. This falls under the title of overdiagnosis. Tumors can develop unnoticed over the years. The affected person may have died without ever knowing about the disease. If he had cancer, he could have avoided tests that would have significantly reduced his quality of life. Like chemotherapy. “On the other hand, there is the potential advantage that, with early diagnosis, the stage of the cancer could be even lower, which can improve treatment success,” explains Ulrich Hacker.
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In principle, however, the success of the treatment is greater the sooner a tumor is discovered. Because then it probably hasn’t metastasized in the body.
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Each person must make their own decision for or against a PSA test. Learn more about early prostate cancer detection here.
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Gunnar Folprecht of the University Cancer Center Dresden sees a good opportunity to use blood tests if there is already a suspicion of cancer. For example, if breast cancer is suspected in a patient, a blood test could confirm the suspicion and warrant further testing or give the green light.
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In patients who are already being treated for cancer, a blood test could prevent unnecessary follow-up treatments. For example, a patient may be being treated for colon cancer. During an operation, tumors in the intestine were removed. After surgical removal, additional radiation should be used to remove any tumors and metastases that may not have been detected. A blood test that detects tumor DNA could show if there are still tumors in the body and avoid unnecessary chemotherapy. A more targeted search is also possible here than with the comprehensive screening test. Because it is often known to which other organs a certain type of cancer spreads. Gunnar Folbrecht is involved in studies investigating the use of such targeted blood tests in colon cancer.
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The future of the Galleri test
The Galleri blood test mentioned at the outset will soon be tested on 140,000 people with no known cancer. Researchers want to find out to what extent the test causes overdiagnosis.
“We need comparative studies for all types of cancer. This way we can find out if an early diagnosis test affects the incidence and mortality rate,” says Fabrice André, oncologist at the Gustave Roussy Institute for Research and cancer treatment.
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