Liquid Biopsy for Prostate Cancer
Traditional biopsy for prostate cancer is performed by inserting thin, hollow needles into the prostate gland to collect tissue samples called cores. The needles are inserted into the prostate through the wall of the rectum. This process is used usually to extract 10-12 core samples. Sometimes the needles are guided to specific areas of the prostate through the use of an ultrasound device, called TRUS, or may be guided with an MRI. These samples are then analyzed under a microscope to look for the presence of cancerous cells, how many there are, and how dispersed they are in each of the core samples.
Why do we need a different way to biopsy?
Researchers have been searching for alternatives to invasive biopsy, or at least an adjunct to traditional biopsy, in part to deliver safer and cheaper diagnostic tools for cancer. While needle biopsies for prostate cancer are safe and usually only present mild discomfort for most patients, many men are often fearful of them. It is common to hear men expressing concerns about pain from traditional biopsies, fear that the biopsy may "spread" cancer or miss detection of cancerous cells.
In addition, men who have to experience multiple biopsies because of rising PSA or before a treatment decision is made often fear the impact of having multiple biopsies on urinary continence or erectile function. Research has shown, however, that men who had multiple biopsies prior to radical prostatectomy do not have longer-term recovery compared to men with only a single biopsy.
Regardless of how safe and effective the needle biopsy is for prostate cancer detection, researchers, healthcare providers, and patients are interested in an alternative to invasive biopsy.
What are liquid biopsies?
Researchers have developed a new technology for liquid biopsy to identify which prostate cancer patients may not respond to standard therapy before initiating treatment. Specific biomarkers that are associated with more aggressive or hormone resistant types of prostate cancer may be detected with this method.1
Liquid biopsies are designed to capture either circulating tumor cell-associated (CTCs) biomarkers or circulating tumor DNA. These cellular fragments or molecules can be captured through a "liquid biopsy." A simple blood draw can be used to gain extensive information about the type of prostate cancer that can help guide treatment decisions.
Multiple studies have demonstrated that quantitative counts of the number of circulating tumor cells (or their biomarkers) can predict prognosis. In addition, genotyping CTCs and circulating plasma DNA can help identify targetable gene mutations and detect cancer recurrence.
The ability to screen patients using a blood sample as opposed to more invasive techniques required for traditional biopsies is a big step forward.
What does this research show for prostate cancer?
A recent study published in Nature Chemistry describes an approach for liquid biopsy using magnetic nanoparticles with the ability to capture DNA that can target CTCs in blood samples. This technique can be used to capture the cells, isolate them from all other cells in the sample, and see if the magnetized cells contain biomarkers associated with known drug resistance.1
Targeting CTCs is important because they carry information from the primary tumor that can inform treatment. Without this type of technology, CTCs are extremely difficult to isolate because they are outnumbered by a billion-to-one by normal cells in an individual's blood. In 2016, a previous study was published in Nature Nanotechnology that first introduced this device and described how it could be used to trap and analyze CTCs.2 The current study builds on the 2016 study by further targeting a specific biomarker within the CTCs.
The cells with the highest magnetic content also have high messenger RNS (mRNA) expression for the biomarker associated with drug resistance. This means that prostate cancer patients that have the highest magnetic content in the liquid biopsy should be considered for treatments other than hormone therapies because they won't respond well to first-line treatment.
This research paves the way for a straightforward and personalized screening tool that can allow healthcare providers to see if a patient will respond well to hormone therapy or not. According to researchers, this method is rapid, highly-sensitive (accurate), and relatively inexpensive, which means it will likely have great potential for clinical uptake once it is FDA approved.
There are "liquid biopsy" tests that look for CTCs biomarkers of gene mutations currently available on the market. These existing tests are not specific to prostate cancer, and many clinicians have different opinions about their diagnostic value. These tests may also not be covered by your health insurance. It is always a good idea to talk about these or any other diagnostic test with your healthcare team before deciding if they are right for you.
How much do you worry about prostate cancer coming back after treatment?