Dr Philip Mack recently presented data in the Proceedings of the American Society of Clinical Oncology Annual meeting suggesting liquid biopsy detected cancer mutations in 85% of all advanced tumours in the largest ever evaluation of circulating tumour DNA (ctDNA) in the blood.

Liquid biopsies are minimally or non-invasive tests used in the diagnosis of lung, colon, and breast cancers. Liquid biopsy is preferred in cases where a surgical biopsy is unfeasible, risky, or where multiple biopsies are required. A liquid biopsy is an easily repeatable technique, which collects tumour-shed minute pieces of ctDNA from the bloodstream. The technique is expected to transform cancer diagnosis by providing clinicians with hassle-free access to information on cancer diagnosis and help in customising treatment according to a patient’s disease condition.

Conventional tumour biopsy is a procedure followed for diagnosis, prognosis, and prediction of response to cancer treatment. Current biopsy procedures used in cancer diagnosis are invasive, and patients are not always in good enough health to undergo surgical procedures, especially in cases where multiple biopsies are needed. This is particularly true in cases such as lung and colon cancers where surgery is necessary to extract the tissue sample for biopsy. Liquid biopsy aims to overcome such complications and challenges in cancer diagnosis. Liquid biopsy is also used when tissue is of insufficient quality or quantity to allow for a broader array of testing.

The emerging liquid biopsy market

Patient adherence, cost-effectiveness, faster recovery time, and avoidance of hospital stay are some of the advantages of liquid biopsy. In June 2016, the US Food and Drug Administration (FDA) approved liquid biopsy test 'cobas Epidermal growth factor receptor Mutation Test v2’ (Roche Molecular Systems) for use in the diagnosis of metastatic non-small cell lung cancer. This test allows for detection of mutations in ctDNA in less than four hours, and also benefits patients who may be too ill or are otherwise unable to provide a tumour specimen.

Companies such as Qiagen, Bio-Rad Laboratories, Fraunhofer-Gesellschaft, and Pathway Genomics are developing new liquid biopsy products for diagnosing various types of cancers. In March 2017, biotech firm Grail announced that it had raised more than $900m from a series of investors, including Amazon, Merck, Bristol-Myers Squibb, and Johnson & Johnson’s venture capital arm to develop blood tests to detect cancer early.

Though liquid biopsy offers promise to achieve greater success in cancer treatment, many aspects such as isolation and characterisation of circulating tumour cells, cell-free circulating DNA, exosomes, and extracellular vesicles needs improvement.