This blood test could save cancer patients unnecessary chemotherapy

What can the new blood test do?

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

Researchers at the Johns Hopkins Kimmel Cancer Center found that a blood test can be used to determine if there are other cancer cells in the patient's body following a tumor removal operation. This could save those affected unnecessary chemotherapy. The physicians published the results of their current study in the English language journal "Science Translational Medicine".

A new blood test can indicate whether there are any other cancer cells in the body after surgery to remove cancer. (Image: Henrik Dolle / fotolia.com)

Side effects of chemotherapy

There is currently no reliable way to determine which patients will have cancer again after surgery. Therefore, early cancer patients often receive post-surgical chemotherapy as a kind of precaution, say the experts. But chemo accompany a variety of serious side effects. In the short term, these include pain, fatigue, nausea and other digestive problems, and often include bleeding and increased susceptibility to infection. 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 surgery, it indicates that microscopic cancer cells remaining in the patient remain, physicians explain. Patients in whom circulating tumor DNA is present 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 on early colorectal cancer patients began as early as 2015. These have shown that the ctDNA test can determine whether patients should be classified into a high-risk group or a low-risk group. The studies were later expanded 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 who need chemotherapy, depending on their risk of returning the cancer.

Cancer often spreads in the body

When a patient is diagnosed with cancer, such as early stage colon cancer, the tumors appear to be confined to the gut, with no indication that the tumors are elsewhere in the body. But after a successful bowel cancer removal operation, about one third of these patients will develop cancer elsewhere in the body in the following years. This shows that the cancer cells have already spread at the time of diagnosis, but could not be detected with current standard blood tests and scans. Treating these patients with chemo after surgery may prevent relapses by removing the microscopic residual cancer cells responsible for the onset of cancer.

When will chemotherapy be used??

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

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)