A liquid biopsy is a blood test designed to detect cancer cells, or DNA fragments from cancer cells, that circulate in the bloodstream. While a liquid biopsy may be useful for several different types of cancer, researchers are particularly excited about its potential for aiding in the diagnosis and treatment of lung cancer.
How Are Liquid Biopsies Being Used for Lung Cancer?
- Detection Lung cancer is often not symptomatic until later stages, when it’s harder to treat. Though screening, in the form of low dose CT screening, is available, few people who are eligible for it (such as longtime smokers) take advantage of it. What’s more, an increasing number of people who have never smoked, and thus are not eligible for screening, are being diagnosed with lung cancer. There is currently no easy and widely available way to screen people for lung cancer who have never smoked. An easy-to-administer, low-cost blood test would make screening easier for both longtime smokers and people who are not eligible for screening.
- Treatment In recent years, a variety of genetic mutations and genetic markers have also been identified on some lung cancer cells, These mutations and markers make them susceptible to treatments known to target them. Each patient’s tumor is different, however. Not all carry the same mutations, or, in some cases, any, so each patient must be screened to determine if their tumors carry markers in order to form the best treatment plan. Traditionally, determining whether and which mutations a patient’s tumor carried involved surgically removing a piece of tissue (taking a biopsy sample) and sending it to the pathology lab in order to determine which molecular targeted therapy the patient would most likely benefit from, says Fred R. Hirsch, MD, PhD, the executive director of the center for thoracic oncology at Mount Sinai Cancer Center in New York City.
More and more often, however, liquid biopsies are being used in addition to standard tissue biopsies to provide doctors with more detail about lung tumors. In certain cases, the blood test may be used in place of a traditional tissue biopsy. A liquid biopsy is often recommended along with a standard tissue biopsy, but doctors might only order the blood test in certain situations. For example, it may be a better option for tumors that are difficult to reach or dangerous to biopsy with traditional methods.
In 2018, the International Association for the Study of Lung Cancer (IASLC), released a statement that outlined how to utilize liquid biopsies for patients with lung cancer. The group said that liquid biopsies should be considered at the time of diagnosis in patients in whom tumor mutations need to be identified. And it’s recommended as an alternative to a traditional biopsy when tumor tissue is scarce or not possible to analyze.
RELATED: Can You Survive Lung Cancer?
How Does a Liquid Biopsy Work?
A liquid biopsy is essentially a blood test. Typically, blood is taken from a vein in the arm. Then it’s analyzed for fragments of tumor cells that may have broken off and entered the bloodstream.
Benefits of a Liquid Biopsy
“The most obvious benefit is that it is much easier for the patients to have a blood test done rather than a surgical biopsy, which always is associated with some risk of complications,” Dr. Hirsch says.
Some other advantages of using a liquid biopsy include:
- It’s safer. A liquid biopsy is a safer test than a tissue biopsy, which can lead to complications such as infection and bleeding.
- It’s not invasive. Tissue biopsies may require surgery, but a liquid biopsy involves only a blood test. Doctors can also take several blood samples over time to test.
- The results are quick. A study published in June 2019 in the Journal of the National Cancer Institute found it took on average nine days to get the results from a liquid biopsy, versus 20 days from a tissue specimen. More recent studies show the results from a liquid biopsy may take even less time.
- The test appears to be accurate. According to Memorial Sloan Kettering Cancer Center, nearly 90 percent of people who tested positive for a cancer mutation on the liquid biopsy had the same mutation confirmed by a tissue biopsy.
RELATED: Why Are Never-Smokers Getting Lung Cancer?
Drawbacks of Liquid Biopsy
Studies show liquid biopsies have a high specificity but a low sensitivity.
That means the blood test is very accurate at identifying a positive result, but a negative result may not be as precise. 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. But more sensitive liquid biopsy technologies are rapidly emerging, says Hirsch.
He adds: “The amount of DNA in the blood might be dependent on the size of the tumor and the stage. Sometimes, it is not enough DNA for reliable examination. Sometimes, [there] is a discrepancy between the molecular findings in the blood and in the tumor.”
RELATED: 5 Early Signs of Lung Cancer
The Future Role of Liquid Biopsies
Going forward, the role of liquid biopsies in treating lung cancer may expand. “I see the role for liquid biopsy in the treatment decision for the individual patient,” Hirsch says. “I also see a future role in monitoring treatment effect and an early determination of when the tumor gets resistant to the given molecular therapy or immunotherapy.” A liquid biopsy may detect increasing abnormal tumor DNA in the bloodstream, indicating tumor progression, for instance, well before it can be seen on a conventional CT scan.
RELATED: New Research Raises the Question: When Is the Best Time to Give Patients With Lung Cancer Immunotherapy?