Simple blood test may help clarify a patient’s cancer
A biopsy is the basis for most cancer diagnoses, and it is the surgical procedure used to remove a tumor so that it can be checked for cancerous cells. Doctors often rely on biopsies to help evaluate the malignancy, stage, origin, and DNA mutations of cancer that may be a target for treatments. Some biopsies are minimally invasive; Others may be more difficult and require stitches or anesthesia. Now, a simple blood test called a liquid biopsy offers another tool that can give doctors a more complete overview of solid tumors. The test is not a substitute for surgical biopsies, but it can provide additional information to help determine specific treatment options. While this cutting-edge technology is only used in certain types of lung cancers at this time, it is being explored as a tool to track and identify other patterns of solid tumors. Arturo Loaiza-Bonilla, MD, MSEd, FACP says:
Cancer cell test
Tumors constantly shed cells that carry their genotype. These cells often end up in the bloodstream. Liquid biopsies are designed to isolate these cells and look for certain genetic characteristics that may indicate cancer and mutations that may lead to tumor growth. “In most cancer-related tests, liquid biopsies look for DNA from metastatic tumors, that is, the parts in the bloodstream of cancer patients,” says Dr. Loaiza-Bonilla. “The test can detect that some fragments have cancer-specific mutations and can help identify weaknesses that we can target to improve treatment options.”
Last year, the US Food and Drug Administration approved the first blood test to detect a genetic mutation found in some patients with non-small cell lung cancer. The test is called the CUBA® EGFR v2 mutation test is designed to identify mutations in the epidermal growth factor receptor (EGFR) gene without the need for a tissue sample. “A liquid biopsy can detect this mutation fairly quickly and effectively so that the patient can benefit from specific treatment that targets the mutation,” says Dr. Alan Tan, MD, medical director of hematology and immunotherapy, oncologist, and hematologist at our hospital near Phoenix. . .
In most cases, liquid biopsies refer to blood tests, but they may also include other types of samples, such as urine, stool, or cerebrospinal fluid. Cologard® for example , is a type of stool test that may provide an alternative to colonoscopy for some patients, especially those at lower risk of colorectal cancer. Dr. Tan says Cologuard is different from other liquid biopsies. “Cologuard is also looking to find elevated levels of the altered DNA, which could be linked to cancer or precancerous,” he said. “With Cologuard, we’re not looking at specific drive mutations, but genetic characteristics that can give you a positive or negative cancer outcome.”
Doctors from Canada, working with researchers at the Eastern Virginia School of Medicine, say they may be close to developing a urine test that can detect proteins only found in prostate cancer patients. Researchers say the test can also reveal whether the cancer is aggressive. “We believe we have found a better method that allows us to predict patients with aggressive or slow-growing prostate cancer using non-invasive biomarkers,” said principal investigator Thomas Kisslinger, principal scientist at Princess Margaret Cancer Center and associate professor at the institute. University of Toronto Science Daily said . “This could eventually help us customize cancer treatment for these patients.”
Liquid biopsy limits
But liquid biopsies have their limitations, too. In some cases, additional procedures may be needed after a liquid sample has been taken to obtain a more detailed diagnosis. Liquid biopsies are also limited in the number of cancers that can be used for testing. Current tests do not detect most DNA mutations, and some tumors do not secrete enough cells into the bloodstream to detect them.
If it is eventually developed as an alternative to surgical biopsies, liquid biopsy has some distinct advantages, Dr. Says Tan and Luisa Bonilla. “The most obvious benefit is the comfort and safety of not requiring a surgical procedure,” says Dr. Tan. And in cases of metastatic cancer, a liquid biopsy can give doctors a broader picture of the overall challenge of cancer. “Because cancer cells mutate and change their DNA as they travel through the body, taking a blood sample can show us bits of DNA from everywhere, unlike a single-site biopsy,” says Dr. Loaiza-Bonilla.
Dozens of clinical trials are underway to determine if liquid biopsies could be a potential diagnostic tool for a variety of cancers, including pancreatic, kidney and ovarian cancers. Dr Tan says, “It is not yet known to judge whether liquid biopsies will replace conventional biopsies. As clinicians, we don’t want to expose our patients to the unnecessary inconvenience and anxiety of invasive procedures. So there is a technique. To replace that without sacrificing quality, there’s no need to think.”
Learn more about biopsies and other diagnostic tools.