Introduction:
- Liquid biopsy, a diagnostic test, is a simple and non-invasive alternative to surgical biopsies which enables clinicians to acquire a range of information about a tumor through a simple blood sample or other body fluid.
- Liquid biopsies can be less invasive than traditional biopsies, which involve removing a tissue sample for analysis, and they can provide a more comprehensive view of the cancer by analyzing cells from throughout the body.
- Liquid biopsies are particularly useful for cancers that have spread or that are difficult to access with a traditional biopsy. However, they are not yet a replacement for traditional biopsies in all cases and are typically used in conjunction with other diagnostic tests.
- Intensive research in liquid biopsy has been conducted over the last ten years in order to produce less painful and more precise individualized therapy. These circulating biomarkers’ molecular analysis can supplement or even replace tissue biopsies. Liquid biopsy has been introduced in clinical practice as a result of this research, particularly in oncology, prenatal screening, and transplantation.
Fig: Milestones in liquid biopsy
Types:
A liquid biopsy is a type of diagnostic test that involves analyzing a sample of a patient’s biological fluids, such as blood or urine, to detect the presence of cancer or other diseases. Liquid biopsies are commonly used to monitor the progression of a disease or to assess the effectiveness of a treatment. They are particularly useful in cases where a traditional biopsy (i.e., a surgical procedure to obtain a tissue sample) is not feasible or may be risky for the patient.
- Circulating tumor DNA (ctDNA) testing: This involves analyzing DNA from cancer cells that have been shed into the bloodstream. ctDNA testing can be used to detect the presence of cancer, monitor the progression of the disease, and assess the effectiveness of a treatment.
- Circulating tumor cell (CTC) testing: This involves analyzing cells that have been shed from a tumor and are circulating in the bloodstream. CTC testing can be used to detect the presence of cancer, monitor the progression of the disease, and assess the effectiveness of a treatment.
- Exosome testing: This involves analyzing exosomes, which are small vesicles that are released by cells and contain a variety of biomolecules, including DNA, RNA, and proteins. Exosome testing can be used to detect the presence of cancer, monitor the progression of the disease, and assess the effectiveness of a treatment.
- MicroRNA testing: This involves analyzing microRNAs, which are small RNA molecules that regulate gene expression and play a role in the development and progression of cancer. MicroRNA testing can be used to detect the presence of cancer, monitor the progression of the disease, and assess the effectiveness of a treatment.
Procedures:
A liquid biopsy is a type of biopsy that involves collecting and analyzing a small sample of bodily fluid, such as blood or cerebrospinal fluid, rather than a tissue sample. The procedure for a liquid biopsy can vary depending on the specific type of fluid being collected and the reason for the biopsy.
It’s important to note that liquid biopsies are generally less invasive than traditional tissue biopsies and may be preferred in certain situations, such as when it is difficult to obtain a tissue sample or when repeat testing is needed. However, liquid biopsies may not always provide as much information as a tissue biopsy, and they may not be suitable for all types of conditions.
Fig: Brain cancer liquid biopsy
Preparation: The patient may be asked to fast or stop taking certain medications before the procedure. They may also be given instructions on how to prepare for the biopsy.
Collection: A healthcare provider will collect the sample of bodily fluid using a needle or other specialized instrument. This may be done through a vein (venipuncture) or by inserting the needle into the fluid-filled cavity where the fluid is located (such as the spinal canal).
Processing: The collected fluid sample will be sent to a laboratory for analysis. The laboratory will prepare the sample for testing and may perform various tests to identify any abnormalities or disease markers.
Interpretation: A healthcare provider will interpret the results of the liquid biopsy and use the information to diagnose or monitor a condition, or to guide treatment decisions.
Liquid biopsy techniques
Cerebrospinal fluid (CSF) liquid biopsy
This type of liquid biopsy involves collecting a sample of CSF, a clear, watery substance that surrounds the brain and spinal cord. A healthcare provider can collect a sample of CSF by inserting a needle into the spinal canal.
Urine-based liquid biopsy
This type of liquid biopsy involves collecting a sample of urine and analyzing it for disease markers or abnormalities. Urine-based liquid biopsies may be used to diagnose or monitor certain types of cancer or other conditions.
Saliva-based liquid biopsy
This type of liquid biopsy involves collecting a sample of saliva and analyzing it for disease markers or abnormalities. Saliva-based liquid biopsies may be used to diagnose or monitor certain types of cancer or other conditions.
Other types of liquid biopsy
Other fluids that may be collected and analyzed in a liquid biopsy include ascites (fluid that accumulates in the abdomen), pleural effusion (fluid that accumulates around the lungs), and peritoneal effusion (fluid that accumulates in the abdomen).
Liquid biopsy is an emerging field with a lot of potential for improving the diagnosis and management of various medical conditions. Here are a few ways that liquid biopsy may be used in the future:
How accurate is a liquid biopsy?
The accuracy of a liquid biopsy can vary depending on the specific type of liquid biopsy being performed, the type of condition being tested for, and other factors. In general, liquid biopsy is less accurate than traditional tissue biopsy, which involves collecting a sample of tissue for analysis. This is because liquid biopsy typically involves analyzing a smaller and less diverse sample of cells, which may not provide as much information as a tissue sample.
That being said, liquid biopsy has the potential to be very accurate for certain types of conditions and tests. For example, liquid biopsy has been shown to be highly accurate for detecting certain types of cancer, such as non-small cell lung cancer and melanoma, and for identifying genetic mutations that can help guide treatment decisions.
The accuracy of a liquid biopsy may also be affected by the quality of the sample collected, the laboratory techniques used to analyze the sample, and other factors. It is important for healthcare providers to carefully consider the accuracy of liquid biopsy and to weigh the potential benefits and limitations of this test when deciding whether it is appropriate for a given patient.
The future of liquid biopsy:
Improved early detection of cancer: One of the main advantages of liquid biopsy is the ability to detect cancer at an early stage, before symptoms appear or before a tumor can be seen on imaging tests. This could lead to earlier treatment and better outcomes for patients.
- Personalized medicine: Liquid biopsy may be used to identify specific genetic mutations or other biomarkers that can help guide treatment decisions. This could lead to more personalized, targeted therapies that are more effective and have fewer side effects.
- Monitoring treatment effectiveness: Liquid biopsy may be used to monitor the effectiveness of cancer treatments and to detect early signs of resistance. This could help healthcare providers adjust treatment regimens as needed to optimize outcomes for patients.
- Non-invasive diagnosis: Liquid biopsy is generally less invasive than traditional tissue biopsy, which can be a significant advantage for patients. This may make it easier to diagnose and monitor a wide range of conditions, including cancer and other diseases.
References:
- MacÃas, M., Alegre, E., DÃaz-Lagares, A., Patiño, A., Pérez-Gracia, J.L., Sanmamed, M., López-López, R., Varo, N. and González, A., 2018. Liquid biopsy: from basic research to clinical practice. Advances in clinical chemistry, 83, pp.73-119.
- Lone SN, Nisar S, Masoodi T, et al. Liquid biopsy: a step closer to transform diagnosis, prognosis and future of cancer treatments. Mol Cancer. 2022;21(1):79. Published 2022 Mar 18. Accessed 8/11/2022.
- Garcia J, Kamps-Hughes N, Geiguer F, Couraud S, Sarver B, Payen L, Ionescu-Zanetti C. Sensitivity, specificity, and accuracy of a liquid biopsy approach utilizing molecular amplification pools. Sci Rep. 2021 May 24;11(1):10761.