A Liquid Biopsy – Is It A Game Changer??

Liquid biopsies are being described as revolutionary for their promises for the future treatment of breast cancer.

Tissue Biopsy Problems

Currently, a surgical tissue biopsy remains the gold standard. However, there are several problems with a tissue biopsy.

• It’s invasive

• It’s challenging to get a biopsy from some areas of the body, like the lungs.

• The turnaround of biopsy results can take about ten days and sometimes more.

• Cancer cells continue to change their shape as long as they’re functioning, which means a tissue biopsy is only a snapshot in time.

• By the time chemotherapy is given, that tumor probably requires new analysis.

• Only one biopsy is given per patient.

• This means as much as 1 in 5 patients receive the wrong medication.

• As much as 70 per cent of BC are found by the patient and not by a biopsy.

• Tissue biopsies are also expensive.

Liquid Biopsy

The principle behind a liquid biopsy is based on the presence of a tumor shedding bits of itself that float into the blood stream.

The tumor shedding leaves one organ, let’s say the breast, and enters the bloodstream to find another organ normally, the lymph nodes, bones, liver, lungs and brain.

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.

So, if you receive a negative result, your doctor will likely order a tissue biopsy to confirm that the results are correct. According to an article published in April 2020 in Cure, some studies have shown the sensitivity of liquid biopsies range from 60 percent to 85 percent

There are three ways in which tumor shedding occurs.

1. Circulating Tumor Cells (CTC): CTCs are cancer cells that split away from a tumor and circulate in the bloodstream. They can sometimes exit the bloodstream and enter other organs, growing into new, metastatic tumors. This tumor shedding in the blood can be measured to determine if a patient has cancer. The more shedding found in the blood, the higher the likelihood of the patient having late-stage cancer. As a result, CTC-based tests can have lower specificity in early-stage settings.

2. Circulating Tumor DNA (ctDNA): ctDNA is DNA that circulates in the bloodstream and derives from cancerous cells and tumors. As tumors grow, cancerous cells die and are replaced by new ones. The dead cells get broken down, and their contents, including DNA. These are released into the bloodstream. Like CTCs, ctDNA can be measured in a patient sample to determine if a patient has cancer. ctDNA is known for its higher sensitivity relative to alternative biomarkers.

3. Exosomes: Exosomes are extracellular vesicles.

What’s a vesicle?

Vesicles are tiny sacs that transport material within or outside the cell.

Exosomes are responsible for cell-to-cell communication and the transmission of diseases. Exosomes are particularly useful as a basis for liquid biopsy, as they are secreted (as in discharged) by living cells rather than by dead ones. As a result, exosome-based assays offer a more comprehensive real-time window into the patient’s health and have higher sensitivity. They also provide logistical benefits because exosomes are highly stable and easy to obtain and distinguish.

Why is this a good thing?

In oncology, the liquid sample is analyzed specifically to find mutations for cancer.

An examination of these bits of tumor floating around in the blood stream potentially provides for more information than a tissue biopsy does. It is particularly helpful for metastatic cancer because it can tell us where the cancer is going. It means LB could help us to stay one step ahead of cancer growth. Baring in mind 90 per cent of BC patients die of metastatic BC this could indeed be revolutionary.

The whole treatment journey could be personalized.

Sensitivity?

Overall sensitivity for the test was 51.5%, with a steady improvement in detection across cancer stages:

• 17% at stage I,

• 40% at stage II,

• 77% at stage III, and

• 90% at stage IV

“Cancer is not a static disease. As the disease progresses, molecular characteristics change over time, and these changes are important to understand how the disease responds to treatment as well as how resistance develops,”

                                                                                       Matthew Bootsma

A researcher in the University of Wisconsin School of Medicine and Public Health and one of the lead authors of a recent report.

“That makes it really important for a clinician to have real-time access to these metrics.”

With a simple blood test

• Liquid biopsies provide the possibility of a quicker and more accurate early-stage cancer detection across a wider range of cancer types.

• Using current standards like surgical tissue biopsy, only about 25% of cancers are detected via screening. The remaining 75% are detected when the patient is symptomatic and from a black perspective, normally in later stages.

• This is, at least in part, why BC has become the number 1 cancer impacting women across the world.

• Plus, liquid biopsies could well be beneficial for detecting cancers that currently do not have proven screening methods, so they currently require invasive tissue biopsies.