Liquid biopsies: The next wave of cancer screening
The annual meeting of the American Society of Clinical Oncology (ASCO), themed "Collective Wisdom: The Future of Patient-Centered Care and Research," was held in Chicago last month. Being the largest and most closely watched cancer conference of the year, this is an ideal forum for drug makers to present new clinical data, and to explore the potential for partnerships.
Given the record number of cancer drug approvals in 2015, it is not surprising that immunotherapy and precision medicine took centre stage at ASCO this year, as the community continues to work on matching drugs specifically to patients' tumours. As ASCO spokesperson Don Dizon puts it, "Precision medicine is not the future of cancer care, it is the present." Precision medicine offers the potential to deliver targeted treatment that has better clinical outcomes, with a better safety profile. This approach has been shown to extend survival in many different cancer types.
A new reality in cancer diagnosis and treatment
The momentum that precision medicine is gaining is truly encouraging. Interestingly, one of the biggest stories at ASCO this year does not revolve around a ground-breaking drug: it is more about a game-changing way of diagnosing cancer patients without the need for painful biopsies.
At the meeting, Guardant Health announced new data from a 15,191-patient study, representing more than 50 types of tumours, pertaining to its Guardant360 "liquid biopsy" technology, a study deemed "one of the largest cancer genomics studies ever conducted." Liquid biopsies, which measure biomarkers in either circulating tumor cells (CTCs) or DNA shed by cancer cells, known as circulating tumor DNA (ctDNA), in blood as opposed to analysing mutations within tissue, have been a hot topic in the field of precision medicine in recent years . Capable of looking at mutations in 70 cancer-related genes, Guardant360 uses next-generation sequencing to analyse ctDNA in patients' blood samples. Researchers found that genetic changes detected in the blood are highly consistent with those identified in traditional tumor biopsies. In the matched blood ctDNA/tumor biopsy samples, researchers also identified mutations not present in tumor biopsy samples that are known to make tumors resistant to currently available targeted agents.
Utilising DNA obtained from blood, liquid biopsy allows patients to be identified in the least invasive way possible, and decreases the need for a surgical biopsy which may be impossible in patients who are too ill to provide a specimen. In addition, multiple samples can be assessed over time, so as to provide a "snapshot" of the genetic alternations that help monitor disease progression, and to leave extra analyses for comprehensive molecular profiling.
Earlier this month, the US Food and Drug Administration (FDA) approved the first liquid biopsy test for the detection of epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer (NSCLC) patients, which are present in approximately 10-20% of NSCLC patients. The cobas EGFR Mutation Test v2 from Roche is the first blood-based genetic test for NSCLC-related mutations, and can be used as a companion diagnostics for Genentech's cancer drug Tarceva (erlotinib).
The bright future of liquid biopsy
Liquid biopsies have been an area of intense study and commercial activity, closely watched by clinical scientists and market analysts alike. There are many companies working on developing liquid biopsies, at least 38 in the US alone. Hence, the outlook for the ctDNA analysis market is promising, and according to a 2015 report from investment bank Piper Jaffray, the market in the US alone is projected at USD29 billion.
Excitement aside, there is still work to do to better understand how best to use liquid biopsies and what role they might eventually play in patient care. There are, of course, mutations that cannot be detected using liquid biopsy, such as for some brain cancer patients. On the scientific front, liquid biopsies are currently primarily conducted by researchers to uncover the secrets of cancer; with no evidence yet from randomised trial that showed liquid biopsies improve patient outcomes, more data is required before the clinical utility of these tests can clearly be demonstrated, and before they can be used routinely in cancer care. One of the challenges of developing molecular diagnostics has been of ensuring adequate accuracy. As with any molecular diagnostic, large studies are essential for evaluating clinical validity and utility; with that established, we can then make crucial decisions how a patient's disease should be treated.
On the other hand, uncertainty around the regulatory and coverage landscape will continue to pose challenges. Given the ease of ctDNA detection, we will in the future inevitably see more and more patients being profiled. The question remains: how best to demonstrate clinical utility and convince payers of the inherent value?
We at IHS have identified such challenges in our recent multi-client study, Pathways to precision medicine: Navigating payer needs and healthcare systems through molecular diagnostics. Individual country chapters of this report are also now available for purchase and immediate access on our IHS Online Store.
Cecilia Chui is a life sciences senior analyst for IHS
Posted on 6 July 2016
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