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This blood test could save cancer patients from unnecessary chemotherapy


What can the new blood test do?

In the future, many cancer patients could be spared the unnecessary side effects of chemotherapy after surgery to remove their tumor. Researchers developed a new blood test that can determine whether cancer cells are still present in the body after an operation.

The researchers at the Johns Hopkins Kimmel Cancer Center found that a blood test can be used to determine whether there are other cancer cells in the patient's body after surgery to remove a tumor. This could save those affected from unnecessary chemotherapy. The doctors published the results of their current study in the English-language journal "Science Translational Medicine".

Side effects of chemotherapy

There is currently no reliable way to determine which patients will develop cancer again after the operation. Therefore, early-stage cancer patients often receive chemotherapy after surgery as a kind of precaution, the experts say. But chemotherapy is accompanied by a variety of serious side effects. In the short term, these are pain, tiredness, nausea and other digestive problems, often bleeding and an increased susceptibility to infections. Long-term side effects can be heart, lung, nerve and memory problems and there are also negative effects on fertility.

What is Circulating Tumor DNA?

When cancer cells die, they release their contents, including cancer-specific DNA, which then floats freely in the bloodstream and is referred to as circulating tumor DNA or ctDNA. If ctDNA is detected after the operation, it indicates that there are microscopic cancer cells remaining in the patient, the doctors explain. Patients with circulating tumor DNA have an extremely high risk of recurrence (almost 100%), while patients with negative test results have a very low risk of relapse (less than 10%).

What types of cancer can be tested?

Studies in early-stage colorectal cancer patients started back in 2015 and have shown that the ctDNA test can determine whether patients should be categorized into a high-risk or a low-risk group. The studies were later extended to women with ovarian cancer in 2017 and will also include pancreatic cancer in the future. The results of the same test could also help scale the dose for patients in need of chemotherapy depending on their risk of cancer return.

Cancer often spreads through the body

If a patient has been diagnosed with cancer, such as early bowel cancer, the tumors appear to be confined to the intestine with no evidence that the tumors are spreading elsewhere in the body. But after a successful colon cancer removal surgery, about a third of these patients will develop cancer elsewhere in the body in the following years. This shows that the cancer cells had already spread at the time of diagnosis, but could not be detected with current standard blood tests and scans. If these patients had received chemotherapy after surgery, relapse could be prevented by removing the microscopic remaining cancer cells that are responsible for cancer return.

When is chemotherapy used?

In the case of colorectal cancer, the decision to use chemotherapy is based on a laboratory examination of the cancer that was removed at the time of the surgery. For example, if cancer cells in the lymph glands are next to the intestine (stage 3 cancer), there is an increased chance that the cancer has already spread elsewhere. Other types of cancer, such as ovarian cancer and pancreatic cancer, use other methods to determine whether chemotherapy is necessary. However, these methods lack precision, the researchers explain. Ultimately, some high-risk patients will not have cancer recurrence because their cancer was cured by surgery alone, while other patients with an apparently low risk develop a relapse. Therefore, many colon cancer patients are currently being treated with six months of chemotherapy - with corresponding side effects, although they actually do not need such treatment. Other patients who could potentially benefit from treatment do not receive chemotherapy because they appear to have a low risk of cancer recurrence.

Test is already being tried in hospitals

Finding and measuring cancer DNA in the blood of patients could revolutionize cancer treatment. The next step is to determine how the test can be used in clinical practice. The new blood test is currently being tested in more than 40 hospitals in Australia and New Zealand. (as)

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