Liquid biopsy: quick, painless, accurate

The word 'biopsy' comes fr ­om the Greek 'bios' meaning 'life' and 'opsis' meaning "sight", which together mean 'to view life'. Since its first  use in 1875, the biopsy test has been used to do just this: provide insight into the inner workings of the body by studying the basis of its existence, the cell and to use this insight to investigate disease, particularly cancer.

A traditional biopsy test involves taking a patient's tissue sample and analysing it under a microscope to check for unusual changes in shape, structure or activity of the cell. Our growing understanding and knowledge of the human genome has enabled us to detect differences between the genome of healthy individuals and those who harbour disease, such as patients with cancer.

Tumour cells have a different genome structure compared to that of normal healthy cells. It is only through tissue biopsies that we can identify malignant tumour cells and decide on the most appropriate treatment. When cancer continues to progress despite treatment, doctors ask for a repeat biopsy which often shows that the cancer is resistant to the chosen treatment. This then guides the oncologist to look for an alternative treatment approach.

Tissue biopsies, however, have some basic problems: they are invasive and require local anaesthesia; they cause discomfort and pain; some tumours cannot be accessed through this method because of their location; in as many as 40% of cases, we cannot collect adequate tissue for molecular testing, and the results take almost a fortnight which delays treatment.

The most common impediment to tissue biopsies is patient resistance because of their invasive nature. Moreover, tumour heterogeneity, that is the differences between tumours of the same type in different patients, or between cancer cells within a single tumour, is not accounted for.

Now, we have a breakthrough that overcomes almost all these problems and issues: liquid biopsy. Its potential came to light when researchers discovered that certain "tumour cell fragments" circulated in the blood of cancer patients.

These fragments of DNA, RNA or proteins released by tumour cells into the patient's circulatory system, could be isolated using a simple blood test and could help us confirm the presence of cancerous activity. Since it is a representative of the tissue from which it has spread, we can deduce the genomic makeup of a cancer tumour by studying these isolated cell fragments.

Faster results

The discovery of liquid biopsies has made it possible for us to analyse tumour characteristics through a quick, almost painless blood test. Liquid biopsy results are available within 3 to 4 days, eliminating treatment delays and increasing the potential for improved treatment.

Beyond simplicity and speed, a liquid biopsy test can, through the use of advanced, technology-driven techniques, help us analyse even small amounts of circulating tumour cell fragments for mutations that are specific to a certain type of cancer. In the case of lung cancer, for example, a liquid biopsy can quickly and efficiently indicate if the tumour cells harbour genetic mutations such as the EGFR or T790M mutation.

Currently, multiple molecular methods for liquid biopsy are being examined to determine
their efficacy, though their use in clinical settings remains low. Some challenges that we still must address before liquid biopsies can enter clinical practice are: optimise and standardise sample collection; implement uniform analytical procedures; and identify the circulating analyte(s) most likely to yield useful tumour information.

Liquid biopsies present a whole new avenue for directing cancer diagnosis and treatment protocols today. Since in cancer each mutation type often warrants adjustments in treatment regimens, liquid biopsies can guide our approach to personalised medicine. The ease with which they can be done makes them useful for real-time monitoring of disease progression.

With liquid biopsies, we are entering an exciting and promising space in the diagnosis, prognosis and overall management of cancer. Our task, for now, lies in building a strong body of clinical evidence for their application in the lives of patients.

The future of cancer biopsy and diagnosis is moving from tissue to liquid biopsy, static mutations to dynamic cancer genomes, genetic descriptions to genomic actionability and prediction to detection of residual/metastatic disease. This enables early detection and intervention, determination of molecular response and secondary resistance in cancer.

(The writer is Director of Research and Development, Triesta Sciences, Health Care Global Enterprises Ltd)

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