A liquid biopsy is a simple and non-invasive alternative to surgical biopsies which enables doctors to discover a range of information about a tumour through a simple blood sample. Traces of the cancer’s DNA in the blood can give clues about which treatments are most likely to work for that patient.
A liquid biopsy test that can detect epidermal growth factor receptor (EGFR ) gene mutations, which occur in 10-35 per cent of patients with non-small cell lung cancer (NSCLC), will help doctors to choose the right treatment for the right patient at the right time.
Much of the early research on liquid biopsies has been in lung, breast and prostate cancers but this technology is expected to have an impact on all types of cancer.
The non-invasive nature of a liquid biopsies, which require only 5 millilitres of blood, means they are much easier to tolerate and the procedure is quicker than a surgical biopsy. The blood sample is then ‘spun down’ to get 2 millilitres of plasma which can be analysed for tumour DNA.
Tolerability and convenience are a major boost for patients. The biggest benefit lies in the potential of liquid biopsies to detect disease progression or treatment resistance long before it would trigger clinical symptoms or appear on imaging scans.
Most cancers have multiple genetic mutations and they may not have the same ones in all parts of the cancer. The tissue samples removed for biopsy may not show all mutations whereas liquid biopsies offer an improved chance of detecting these genetic changes.
“Liquid biopsies could be a game-changer in cancer testing,” said Miro Venturi, Roche’s Global Head of Diagnostics Biomarkers. “In terms of patient acceptability and disease management, the benefits of non-invasive, quick and easily repeatable tests are clear. And in the longer term, liquid biopsies may ultimately be used to catch signs of cancer early, before symptoms arise. This could make a significant difference to the way we understand and treat cancer.”
“From a treatment perspective," comments Lukas Amler Senior Director, Oncology Biomarker Development, Genentech, “the increased access to liquid biopsies, especially for patients that do not have tissue available or cannot undergo a new invasive biopsy, could significantly increase the number of patients who will benefit from powerful targeted medicines, particularly in lung cancer. Tissue could also be reserved for other novel testing for example for cancer immunotherapy where currently there are no blood tests available.”
The power to improve progression and survival rates will be the ultimate determinant of whether liquid biopsies become a leading diagnostic tool.
Liquid biopsies have the potential to revolutionise cancer care. However, there are challenges to the widespread use of this new approach and there is still a place for tissue biopsies. Far from being redundant, taking and testing tissue samples remains the gold standard.
For liquid biopsies, it is still relatively early days and some questions still need to be answered. For example, to what extent does test accuracy vary among tumour types and stages of disease? Does the liquid biopsy provide a representative sampling of all the genetic clones in a tumour or is there a bias to specific sub-regions? Researchers are currently working to answer these questions.
The liquid biopsy will not replace the tissue biopsy in the foreseeable future”, says Joakim Jagorstrand, Lifecycle Leader for Genomics and Oncology at Roche Diagnostics. “However, liquid biopsies will complement the tissue biopsy allowing more patients to be tested. The issue is that many times there is just not enough tissue to test on. This novel, minimally invasive technique has the potential to change the prognostic and predictive landscape for lung cancer genotyping and impact patient management. I think we are close, but we are not completely there yet. More real world clinical studies and comparisons are needed to fully explore the potential of plasma based testing. It is an exciting opportunity, a win for the patient in many ways and Roche is one of the world leaders in developing such tests.”
More validation in clinical trials is required on the value of liquid biopsies in the medical setting. And, while liquid biopsy informs treatment decisions in lung cancer with an epidermal growth factor receptor (EGFR) mutation, targeted therapies do not exist for all cancers. Are liquid biopsies the best option in diagnosing and monitoring these cancers? What if any role do liquid biopsies play in informing treatment decisions in the emerging field of immune oncology? These are questions that scientists and clinicians continue to explore.
“Using a blood test rather than relying on tissue would be a breakthrough as sometimes a (surgical) biopsy doesn’t take enough tissue,” says Dr Jesme Fox, Medical Director of The Roy Castle Lung Cancer Foundation, a lung cancer charity. “The science isn’t quite there yet but there is hope for the future.”
However, as scientific knowledge advances, researchers are learning more about the potential of liquid biopsies to detect mutations, suggesting that the promise and power of this diagnostic technology could be truly game-changing.