On our radar: an emerging cancer screening innovation
Liquid biopsy has potential to screen for pre-symptomatic cancer cells
Everyday, scientists are on the hunt for non-invasive ways to reliably detect the presence of cancer at an early, curable stage. In cancer research, innovations come and go, but there’s one test in development that is showing great promise. It’s called liquid biopsy and it’s something my colleagues and I are following closely.
When a person has cancer, the tumour sheds cells (they’re called circulating tumour cells) and fragments of DNA into the bloodstream. A liquid biopsy is a simple blood test that can detect these cells and pieces of DNA.
Capture circulating tumour cells
Liquid biopsy is already part of some current treatment protocols. Tests to look for certain circulating tumour cells can help doctors understand how well a patient’s treatment is working and assess overall prognosis. However, scientists are even more excited about the potential value of testing the fragments of circulating tumour DNA using genetic sequencing technology. There are two reasons why.
May alter cancer treatment
First, liquid biopsies have the potential to alter how we approach cancer treatment. Current protocols involve taking a tissue biopsy (which has inherent risks and discomforts), testing the tumour tissue for specific DNA markers, and then using a therapy targeted at these DNA markers.
However, cancer cells are not stable. In fact, they are notorious for mutating.
Since liquid biopsy is a non-invasive blood test, it promises to assess how people are responding to treatment in ‘real-time’, enabling a more catered and appropriate treatment protocol. This would mean we could stop treatments that aren’t working, avoiding unnecessary side effects, and move on to other targeted therapies without wasting time. In the long term, it may also help us to develop a better understanding of how cancer metastasizes and why some cancers are resistant to certain therapies.
Screening tool for pre-symptomatic cells
Second, there is the potential to use liquid biopsy as a screening tool that can detect the presence of a tumour before it causes symptoms or can be seen on conventional imaging or cancer screening techniques. By screening for unique DNA sequences specific to certain types of cancers the blood screening tool aims to not only detect the cancer, but also to pinpoint tumour location and staging/prognosis.
Ultimately, scientists hope to develop a pan-cancer screening test, an all-in-one simple blood test that screens for the presence of early pre-symptomatic cancer.
Risks and opportunities
In medical innovation, challenges are to be expected. Perhaps not all types of cancer shed pieces of DNA into the bloodstream. False positives could lead to unnecessary invasive testing and stress on the patient. There is also the risk of picking up and treating cancer that would never have progressed, or would progress so slowly it would never cause clinical concern.
But despite the challenges, the scientific community seems to agree, the only way to make a dent in cancer mortality is to find it in asymptomatic individuals. And, although there is much work to be done, there is good reason to get excited about the potential of liquid biopsies as a non-invasive way to detect early-stage cancer and to monitor real-time response to treatment.
Jill Furnival is a genetic counsellor at Medcan, and freelances as a medical writer for health-related organizations such as the the American Heart and Stroke Association.
