Presenter, Dr Kat Arney, is in her element in this fascinating Genetics Unzipped episode on liquid biopsies entitled: 'In the blood: using circulating DNA to detect and monitor cancer'. It's not surprising, since her own PhD was in epigenetics, she's authored a book on cancer, 'Rebel Cell: Cancer, evolution and the science of life' (see BioNews 1100), and personally knows several of the key players in the liquid biopsy field.
Testing for cancer using circulating tumour DNA from a blood sample, called 'liquid biopsy' is the so-called 'holy grail' of cancer diagnostics. The idea of liquid biopsies is to diagnose cancer from a simple blood sample, being less invasive than a tissue biopsy and more sensitive than a scan. The liquid biopsy detects genetic material shed by cancer into the bloodstream, and epigenetic analysis has provided an upgrade: If genetic analysis is reading a whole library book, epigenetic analysis is reading the back cover – a summary page stamped with the shelf information.
In this episode, sponsored by AstraZeneca, Dr Arney interviews three cancer experts – a top academic, an R&D leader at AstraZeneca and the president of GRAIL Europe.
Professor Charles Swanton, chair of personalised medicine at University College London, and a group leader at the Francis Crick Institute, talks about the difficulties and dangers of tissue biopsies. He sees huge potential for testing patients after surgery to see if any cancer remains, determining whether they need chemotherapy or not. He also mentions the limitations - the main one being that small cancers are more likely to be missed by a blood test. 'Nothing is perfect, and we can't sample the patient's entire blood volume', he acknowledged.
Dr Arney also speaks with Dr Susan Galbraith, executive vice president of AstraZeneca's Oncology R&D division, to find out more about where circulating DNA comes from, and what it can tell us about cancer. She explains the shortcomings of current imaging tests (MRI and CT scans), which can't detect small clusters of cells remaining after treatment. Blood tests may offer a more accurate and more affordable alternative. She is particularly excited by early detection, such as that being developed by GRAIL, which will improve treatment and outcomes for patients.
It is fitting that this podcast also speaks to Sir Harpal Kumar, the president of GRAIL Europe - the not-so-humbly named Illumina spin-out company that is developing epigenetic liquid biopsy tests. Instead of the classic tests which look at genetic mutations in circulating tumour DNA, GRAIL looks at epigenetic markers (called methylation) which give deeper information on cancer location and type. Sir Harpal speaks about the potential of their technology to monitor cancer patients and screen populations – a task which demands pinpoint accuracy. He explains, 'In population screening you want to be able to detect as many cancers as possible, but you want to do it with a very low false positive rate… what you don’t want to do is tell lots of people they might have cancer when actually they don't'.
Dr Arney comments on how fast the field of epigenetics has evolved, citing how the technologies she used during her PhD 20 years ago were not very sophisticated. At that time, DNA sequencing was a laborious task and even from my own epigenetics experience just ten years ago, I have to agree! Sir Harpal made the point that epigenetic sequencing has not only recently become easier, it has also become much cheaper too (relatively speaking that is - GRAIL's test price is $949 (£823)).
I was surprised that the Theranos scandal wasn't mentioned, although I feel that perhaps it is for the best that this particular stain is scrubbed from the field. Theranos fraudulently promised technology for blood testing of multiple diseases, including cancer. Unlike Theranos, legitimate companies like GRAIL are partnered with huge pharmaceutical companies and accumulating plenty of transparent clinical trial data. In fact, there is a current UK clinical trial ongoing called the NHS-Galleri trial – participation is now closed but many listeners may want to keep an eye out for future trials. I know I will be!
As a fan of the Genetics Unzipped podcast, I've enjoyed and reviewed other episodes (see BioNews 1087), but one this is a standout. I'd recommend it for all of those with an interest in cancer. And if you eschew podcasts for the written word, you can read all the interviews online on the Genetics Unzipped blog.
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