8/20/2023 0 Comments Liquid notes vs![]() Alternately, the sample may not represent mutations that actually are present in a tumor. CTCs or ctDNA may be from a source that is no longer a threat, or the genes present in them are from a tiny fraction of the tumor. This indicates that certain mutations may be under or over represented in a random sample. For example, a study on prostate cancer reported that two separate liquid biopsy companies found matching mutations for only 7.5% of patients ( Mone). Thus, liquid biopsies are more advantageous to prove an overview of the mutations present in each of the tumor sites, or when tumors are in an unreachable area where tissue cannot be collected via needle or surgical methods and cfDNA must be used.Ī drawback is that cfDNA in liquid is extremely limited and detection sensitivity is low. It is not practical, or often possible, to collect tissue from each tumor for analysis. Liquid testing also uses a much smaller sample and has a significantly quicker turnaround for results compared to tissue biopsies, partly due to WGS automation processes.Īnother area where liquid biopsies excel is when a tumor has metastasized, meaning it has spread to multiple sites in the body ( Parnell). ![]() In all of these cases, WGS methods are used to detect genetic alterations of interest. Furthermore, liquid biopsies are vital in precision treatment and tracking relapse in patients with remission ( Gen News). They can be uniquely used as a screening tool for early detection either by testing the entire sample for mutations, or looking for specific mutations in the sample. Liquid biopsies utilize genetic sequencing for many purposes in oncology. Research has sequenced exons, or sections of DNA, and found markers associated with types of cancer, such as the protein HER2 in breast cancer ( Shtivelman). A common method of analysis is whole genome sequencing (WGS), which maps an organism’s genome and tracks specific mutations associated with cancer. Tissue or liquid sample collected in a biopsy is tested for cancer by analyzing genetic material. This is the case of formalin fixation, which displays higher levels of a certain allele frequency range and results in false positives for cancer diagnosis ( Ilie & Hoffman). Unfortunately, preservation methods involve the use of chemicals that may degrade the effectiveness of a sample. An unfortunate challenge in tissue that has not been preserved is tissue necrosis, which occurs quickly in tumor cells ( Parnell). Once extracted, the tumor specimen is then preserved and analyzed for mutations. As a result, side effects can include risk of infection, internal bleeding, or prolonged recovery time. Specimen extraction from the body may require surgical methods. Techniques can involve needles, endoscopic tools, or excision using a sharp utensil to cut tissue. An anesthetic may be used: local to numb area of extraction for pain, or general to make the patient unconscious. This specimen is removed either directly from a tumor or from bone marrow. Tissue biopsies require solid matter from the body. In oncology, the liquid sample is analyzed specifically to find mutations for cancer. When a liquid biopsy is performed as a screening tool, it is possible that all of the cells will be analyzed to find any markers that match diseases. While all of these methods are considered less intrusive compared to tissue biopsies, cerebrospinal fluid (CSF) is extracted using a spinal tap in a relatively painful procedure. Liquid biopsies often collect fluid samples in traditional non-invasive ways blood samples are drawn intravenously, urine is collected in a sterile cup, and saliva is swabbed in the mouth. Also significant for analysis are circulating tumor cells (CTC), which shed from a primary tumor. In oncology, some of the most important cfDNA are circulating tumor DNA (ctDNA), which come from a cancerous cell. It is theorized that when cell death occurs, the cell releases DNA into the fluids they are associated with. Liquid biopsies work by measuring cell-free DNA (cfDNA) in a sample of fluid from the body. (Right: Comparison of Biopsy Methods Gen News ). The initial component in both of these biopsy methods is the extraction of matter to be analyzed. Tissue Sectioning and Microarray Construction.
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