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Do you know what’s liquid biopsy? Just realised i own this cancer stock that made this




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5 JUL 2023 AT 4:00 AM SGT


Liquid biopsy is a relatively new and innovative approach to diagnosing and monitoring cancer.
Done via a blood sample, it is currently used in tandem with traditional tissue biopsies. The aim is to detect and analyse genetic material that tumours may release into the bloodstream so doctors can understand the cancer better and match patients with more effective therapies.
The genetic material in question is circulating tumour DNA (ctDNA), which is produced when tumours shed small fragments of their DNA into the bloodstream.

But how does the ctDNA, also known as cancer DNA, get into your blood?
Dr Steve Olsen, chief medical officer, Asia, Middle East and Africa (AMEA) of Guardant Health a precision oncology company explains: “When cells, including cancer cells, rapidly divide, some grow while others die. The cells that die release all their contents into the bloodstream, such as amino acids, chemicals and DNA.”
Genomic sequencing is used to detect traces of cancer DNA in the blood, which is helpful in examining genetic alterations present in the tumour.

Dr Olsen, whose company makes such a test, adds: “Our assay and other comprehensive liquid biopsies work by identifying cancer DNA and distinguishing it from normal DNA.”


Liquid biopsies can complement traditional tissue biopsies by offering a less-invasive alternative – through an intravenous blood draw – to examine cancer DNA especially if more tissue samples are needed for other tests.

How cancer patients can benefit from liquid biopsies​

According to Dr Olsen, the only liquid biopsy approved in Singapore is specifically designed for people with late-stage or advanced cancers.

This assay can help to guide the course of treatment when the cancer has spread (metastasised) and is no longer considered curable by traditional methods.

Typically, the conventional method of testing a tissue biopsy looks at each gene individually to identify mutations before treatment is recommended. However, this process can be time-consuming and may take more than a month.

Citing the example of non-small cell lung cancer, Dr Olsen says there are over 10 different genomic or gene-based biomarkers that are recommended to be tested because there are targeted therapies associated with those genetic alterations in the cancer.

“Doctors now have the option to use one test to look for all the possible mutations that are associated with treatments,” he explains. “Some of the cancer treatments will only work if there is a particular mutation. The idea is, if one of these mutations exists, then the patient is eligible for a particular treatment.”

Instead of the lengthy, conventional testing procedure, which tests tumour tissue obtained from a biopsy for the presence of changes in individual genes and could take more than a month, another method which takes as little as 10 days is available. Comprehensive genomic profiling (CGP) through a liquid biopsy that tests for all the possible mutations simultaneously, from one draw of blood does just that.

Liquid biopsies not only identify cancer mutations before the start of treatment but can also help to inform next steps much faster when the current regimen may no longer be effective in staving off tumour growth.

“Cancer cells do mutate in response to treatment,” points out Dr Olsen, in addressing why treatments often need to be adjusted along the way as things change.

With real-time ctDNA information, doctors can quickly assess the efficacy of ongoing treatments and make informed decisions about modifying or changing therapies to improve patient outcomes.

“This will help doctors select targeted therapies while allowing them to monitor patients’ responses to immunotherapy or targeted therapy,” he says.

Other types of liquid biopsy assays that are in the research stage include those that detect residual cancer in early-stage curable cancer as well as early detection and screening of cancers in otherwise healthy individuals.


Detecting residual cancer is important as the presence of ctDNA after treatment or surgery could mean that there are still small traces of cancer cells that have remained in the body. Known as minimal residual disease (MRD), the detection of MRD can help doctors determine if further intervention such as chemotherapy should be considered to prevent a relapse.
“Because it is so microscopic or hidden, it is possible that there is still cancer remaining that the surgeon was not able to see,” explains Dr Olsen. “In that situation, a liquid biopsy can help doctors to decide if they should do something extra beyond the surgery or if they should try another course of treatment.”
This is currently being trialled in cancers that are common and highly curable such as colon and breast cancer.
As for the early detection and screening protocols, which are also at the clinical research stage, Dr Olsen says the liquid biopsy assay must be very sensitive in order to find the cancer DNA at very low concentrations in the blood.
This can help patients become aware of their cancer even before it becomes symptomatic or even life-threatening.

Current limitations and the future ahead​

While liquid biopsies can be helpful in one’s cancer journey, Dr Olsen recognises their limitations. For example, when it comes to early detection, the challenge is to determine what the right solutions or next steps are when someone receives a positive test result.
“At this point, we are aware of the concerns about how to confirm if it is truly positive and what should be done with that information,” he acknowledges. “That is why we are careful about how we design these studies and ascertain what the appropriate follow-up is, especially when healthy people receive a positive test result.”
In the case of colon cancer, typically a slow-growing cancer, Dr Olsen notes that a colonoscopy should be enough to rule out the possibility of cancer. However, false positives can get more complicated for cancers that do not have screening tests, such as pancreatic cancer.
“Pancreatic cancer is very aggressive,” explains Dr Olsen. “Even if it is a false positive – you don't find it in the initial scan but tested positive for it – most doctors will likely follow up vigilantly with the patient.”
Dr Olsen explained that for metastatic disease, lack of ctDNA detection (a false negative result) is associated with a better prognosis. Metastatic cancers that do not release significant amounts of DNA into the bloodstream are less aggressive. People with such types of cancers tend to live longer.
Another scenario is a false negative result when screening healthy individuals. This means that the person goes on to develop cancer even though the ctDNA test was negative. This is expected to be very rare, says Dr Olsen.
“Most healthy people who undergo screening do not have cancer, therefore a negative result is expected most of the time. However, cancer may be present even if tumor DNA is not detected in the blood. This is one of the reasons that, until we learn more, liquid biopsy should complement but not replace standard cancer screening procedures,” he adds.
Liquid biopsies are a non-invasive and low-risk procedure, which reduces the patient burden. Patient access to these tests can increase access to important clinical information, potentially lower overall healthcare costs, and possibly lead to better clinical outcomes as more patients are matched with effective therapies, notes Dr Olsen.
“There has been encouraging feedback from doctors and patients who appreciate the convenience, rapid turnaround time and not having to go in for an additional surgical procedure,” he says.
For more information, visit Guardant Health.


According to Dr Olsen, the only liquid biopsy approved in Singapore is specifically designed for people with late-stage or advanced cancers.
But lucky USA people cancer survivor with no melanoma cancer now said he is using ctDNA test for surveillance to detect cancer recurrence. Said no problem to claim it under insurance some more.