Mammograms have been the gold standard for breast cancer detection since the mid-1970s, but they aren’t foolproof—especially for people with dense breast tissue.
Now, promising research from scientists at the University of Southern California has shown there might be an easier and more equitable way to find early signs of breast cancer—liquid biopsies.
Dorraya El-Ashry, PhD, chief scientific officer at the Breast Cancer Research Foundation, told Verywell that the term “liquid biopsy” covers a large set of tests that look for abnormalities in the blood that could be signs of cancer.
“It’s really just a blood draw that’s looking at any number of biomarkers,” said El-Ashry. “We talk a lot about biomarkers for cancer, but they are used for other diseases as well.”
While the new study was small, the findings will likely inspire more research and eventually may lead to the widespread use of liquid biopsy testing.
For the study, the researchers looked at 100 patients from 2013 to 2017. Of the patients, 60 had either early- or late-stage breast cancer. The other 30 patients were healthy.
After taking blood from the patients, the samples were looked at using a special method (assay) that can pick up biomarkers called oncosomes, which have tell-tale signs of the cancer cells they come from.
What Are Oncosomes?
PhD candidate Sonia Maryam Setayesh, a co-author of the study, told Verywell that oncosomes are kind of like a snake shedding its skin.
Oncosomes are secreted from tumor cells to communicate with other cells. They get made through a process called “blebbing,” where a part of the cell comes out (exuded) and becomes separate from the original (tumor) cell.
“They have a similar proteomic profile, and they harbor genomic content similar to the originating tumor cell,” said Setayesh. “They just don’t have a structured or organized nucleus.”
According to Setayesh, researchers in previous studies have only been able to find tumor cells or cell-free DNA—both of which are signs of late-stage breast cancer.
Oncosomes, on the other hand, occur in higher volumes in the early stages of breast cancer development, which is why they can be a marker for early detection.
“This influx of oncosomes in early-stage cancer really allowed us to not only separate it from late-stage cancer but from normal donors,” said Setayesh, “And then to be able to actually differentiate a breast cancer patient that is not yet metastatic”—that is, a patient whose cancer has not spread.
Can Liquid Biopsies Catch Other Cancers, Too?
Since oncosomes share genomic material with their host cells, they can be used to identify several different cancers.
The new study specifically looked for breast cancer markers, but blood tests have been used to detect pancreatic, colorectal, and bladder cancers, too.
According to El-Ashry, tests known as multi-cancer detection tests can look for several different cancers in the same blood draw.
While liquid biopsies might be used for early cancer detection in the years to come, El-Ashry said they are already in use now for a different reason—monitoring treatment.
For example, El-Ashry said “if a stage two and three breast cancer patient is getting neoadjuvant chemotherapy,” the test could be used to see if “there is either a decrease in circulating tumor cells or cell-free DNA as a response to treatment.”
Or if a patient has not responded, El-Ashry said the test “can help them determine switching treatments and tailoring which treatments to use.”
Easier Access to Early Detection
El-Ashry cautioned that more research and testing are needed before liquid biopsies could become widely used for early detection, but they are certainly an exciting prospect.
“Any tissue biopsy is only a window into that slice of tissue that you took out and the cells that are there,” said El-Ashry. “Liquid biopsies allow you to look at the cellular heterogeneity that exists in many cancers—it’s giving a window into additional information that you don’t get from traditional screening or biopsy.”
Liquid biopsies could also be more accessible to people who can’t get mammograms, for example, because they don’t live near a center that has the technology.
Adding liquid biopsies to standard screenings is likely still years away, but for now, they’re a beacon of hope for cancer researchers who are looking for ways to level the health playing field.
