What is Liquid Biopsy?


What is liquid biopsy?


 Imagine a simple blood test being used to track disease status or to check if a patient is responding to treatment… Now, you might think “There are already blood tests available, aren’t there?” Yes of course, these existing tests are based on detecting certain proteins in our blood, analyzing the changes in their levels. But such tests are not available for all diseases. For diseases such as cancer, especially solid tumors such as breast cancer, initial analyses to identify the type of the tumor or the particular molecular makeup of the tumor, is done by tumor tissue biopsy. A biopsy involves taking a small section of the tissue of interest for further analyses. But how do we know if a particular treatment works? And what about those tumors that cannot be accessed or those which may not show any visible changes? What if a tumor just changes its molecular pattern and survives in spite of treatment? For the past few decades, researchers have been trying to answer these questions through liquid biopsy. 

Liquid biopsy is the analysis of blood (most commonly used) or other biofluids such as saliva, sweat, urine or cerebrospinal fluid. The tests commonly analyse cells, circulating nucleic acids or microvesicles present in the biofluids. Since, liquid biopsy-based analyses are non-invasive and easy to sample, they are more convenient to use in case of repeated testing, such as for monitoring treatment response and checking for disease relapse. But they also have some disadvantages. Some biomarkers may not be at detectable levels in blood as compared to tumor. Also, there is currently a lack of consensus among the technical approaches to liquid biopsy, which is why it is not routinely used for some diseases. Nonetheless, it is an evolving field with ongoing research showing its clinical potential. It may one day, prove to be a reliable and powerful tool for non-invasive disease management. Each component of liquid biopsy - circulating tumor cells, circulating nucleic acids and microvesicles - will be described in detail in the following posts.

The infographic below gives an overall summary about liquid biopsy:



References

1. Palmirotta R, Lovero D, Cafforio P, Felici C, Mannavola F, Pellè E, et al. Liquid biopsy of cancer: a multimodal diagnostic tool in clinical oncology. Ther Adv Med Oncol [Internet]. 2018 Aug 29;10. 

2. What is a Liquid Biopsy? [Internet]. Available from: https://www.healio.com/hematology-oncology/learn-genomics/introduction-to-liquid-biopsies/what-is-a-liquid-biopsy


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