The sampling and analysis of non-solid biological tissue, primarily blood, is known as fluid biopsy or fluid phase biopsy. Liquid Biopsy is a groundbreaking technique that aids in the early detection of cancer and the monitoring of treatment effectiveness. Multiple blood samples over a period of time may also help doctors understand the molecular changes taking place in a tumour. It can also be done more frequently, allowing for a more accurate tracking of tumours and mutations over time. By taking multiple liquid biopsy samples over a few weeks, it can also be used to validate the efficacy of a cancer treatment drug. Patients may find the technology useful in monitoring relapse after treatment.
AIM OF LIQUID BIOPSY
- Cancer screening and early detection
- Estimation of the risk for metastatic relapse or metastatic progression (prognostic information)
- Therapy stratification and real-time monitoring
- Determination of therapeutic targets and mechanisms of resistance
- Gaining a better understanding of the biology of metastatic spread
WORKING OF LIQUID BIOSPSY
- Traditionally, diagnosing cancer entails removing tissue from a suspected organ and testing it for cancer. Depending on the location of the cancer, invasive surgery may be required.
- Liquid biopsies, as these tests are known, entail catching free-floating tumour pieces or specific pieces of tumour DNA in the blood. The DNA is then examined to see if it contains mutations that have been linked to certain types of cancer.
- Circulating tumour cells, microvesicles such as exosomes, and cell-free circulating tumour DNA, CG DNA, are all released into the bloodstream by solid cancers. The term "liquid biopsy" has been coined to describe the process of analysing all of these Circulating biomarkers. Apopotic and necrotic tumour cells release fragmented DNA into the circulation, which accounts for the majority of circulating tumour DNA.
- Tumor cells release ctDNA into the bloodstream when they die.
Because cancer mutations in ctDNA are similar to those found in traditional tumour biopsies, they can be used as molecular biomarkers to track disease progression. Next-generation sequencing (NGS) or PCR-based methods such as digital PCR can be used to purify and analyse ct DNA.
TYPES OF LIQUID BIOPSY
- CTCs (circulating tumour cells) and ctDNA (circulating tumour DNA) are collected for cancer research.
- Circulating endothelial cells (CECs) are sampled to diagnose a heart attack.
- Cell-free foetal DNA (cffDNA) is extracted from maternal blood for prenatal diagnosis. It is also possible to extract and analyse amniotic fluid.
APPROACHES TO LIQUID BIOPSY
- CTC (circulating tumour cell) tests, which examine whole tumour cells in the blood.
- Circulating tumour DNA (ctDNA) tests, which look for DNA released into the bloodstream by tumour cells.
ADVANTAGES OF LIQUID BIOPSY
- When compared to tissue biopsy, liquid biopsy is significantly less invasive.
- The results of the test are usually available much sooner than the results of a standard tissue biopsy. It is possible to make an early diagnosis using liquid biopsy.
- Liquid biopsy can be used to predict the likelihood of relapse or progression of metastatic disease.
- Liquid biopsy could help with therapy stratification and monitoring in real time. It may be able to identify therapeutic targets more effectively.
- The liquid biopsy test has an advantage over tissue biopsy in terms of ease and frequency. The test is simple to repeat if necessary, and it can be used as often as needed to track the patient's progress.
- Liquid biopsy is typically less expensive than tissue biopsy.
LIMITATIONS OF LIQUID BIOPSY ASSAYS:
- Liquid biopsy is not yet regarded as a standard diagnostic test: Although these assays are becoming more widely used, tissue biopsy remains the gold standard for confirming and diagnosing diseases, including various cancers, as well as determining disease characteristics. At present, liquid biopsy is not used as a replacement for the tissue biopsy test but used primarily as a complimentary test to tissue biopsy.
- More evidence of the test's clinical utility is required. The liquid biopsy test is currently not widely used in the medical community.
- It necessitates the use of specialised laboratories and personnel.
- More research is needed to determine the test's accuracy and ability to identify different tumour types. It's unclear whether the liquid biopsy provides a representative sample of all genetic clones within a tumour or if it favours specific tumour sub-regions.
- There are still issues with test sensitivity. Low concentrations and erratic recovery make detection difficult.
- Liquid biopsy is becoming a more important and practical molecular diagnostic technique, both for initial diagnosis and follow-up.
By 2035, India's total cancer disease burden is expected to have risen significantly from around 1 million new cases per year in 2012 to more than 1.7 million per year. With such a concerning trend, it's becoming more important than ever to shift to new treatment diagnostic approaches.