Liquid biopsies move towards becoming the preferred method of monitoring tumors
It’s no secret that cancer diagnostics play a central role in the realm of medical laboratory science. There’s a consistently growing need for medical laboratory professionals (MLPs) to delve deeper into this field and create diagnostic tests that are precise, efficient and affordable—and this need will not vanish any time soon.
With technology constantly evolving, it should come as no surprise that cancer diagnostics are changing too. Biopsies have long been a dreaded mainstay of cancer diagnostics; however, clinicians and patients alike are well aware that these tests could use some upgrades. Admittedly, biopsies as a whole are unavoidable in identifying cancer: They confirm cancer diagnoses, identify the cell type of the tumor and determine whether a tumor contains particular genetic alterations that could qualify the patient for specific targeted therapies.1
A Need for Change
Despite their usefulness, traditional biopsies are far from pleasant for the patient and leave much to be desired for the clinician. They require invasive procedures for which some patients may not be eligible for due to poor health or because of a tumor’s location. Further, after the initial analyses of biopsy samples, there may not be enough remaining tissue to perform comprehensive molecular profiling.1
These issues have not gone unnoticed, and many MLPs are moving in a new direction. “Liquid biopsies,” also known as cell-free DNA (cfDNA) assays, are tests that assess changes in genetic material shed from tumors into the blood to identify or monitor tumors, and are well on their way to becoming commonplace in medical laboratories.1
Of course, blood-based testing isn’t new to cancer diagnostics. “There are a variety of different biomarkers that have been used to assess tumors in patients or predict the likelihood of cancers,” said Frederick Racke, MD, PhD, medical director of hematology/oncology and coagulation at the Quest Diagnostics Nichols Institute. “However, with the significant advances in DNA technology that are occurring, there’s really a fundamental shift offering in the types of tests and the information that can be acquired through the so-called liquid biopsy.”
Quest Diagnostics isn’t new to the world of plasma-based testing, having introduced its Leumeta assays in 2005 to test for certain hematologic cancers. “It might seem counterintuitive to use plasma-based testing for hematologic malignancies which are often bloodborne, but it turns out that certain types of hematologic malignancies, such as the myeloproliferative neoplasms that are JAK2 driven, are much more sensitively detected through plasma-based testing.”
While liquid biopsies aren’t brand new, at the moment, their uses are limited. “Currently, the common use of a liquid biopsy would be, say, for non-small cell lung cancer in a patient who has been identified as having a targetable mutation, like EGFR,” said Racke. “Largely, plasma-based testing has been used to identify resistant mutations—particularly EGFR mutation T790M—in the blood that would inform if the patient does indeed have resistance to the frontline EGFR inhibitors and would be eligible for second-line targeted therapies that overcome the T790M resistance.” Further, many liquid biopsies are still in trial stages.
Because the uses of liquid biopsies are still being discovered, funding these tests is still a challenge. “Part of the struggle we face is the reimbursement climate,” Racke admitted. “Liquid biopsies have not yet gained widespread acceptance in the payer setting. But once there is more and more acceptance by key societies and opinion leaders, there will be more access to such testing for a broader scope of patients than just, for instance, whose who are in academic settings or clinical trials.”
Yet many MLPs, including those at Quest Diagnostics, are working to develop new liquid biopsies with different uses—but these new tests won’t emerge for a bit longer. “As you can imagine, these kinds of fundamental shifts in technology take a lot of development,” said Racke. “Our strategy, broadly, is to develop a test that will focus on the most common recurrent mutations in the moist common adult tumors that have very clear and defined therapies and will allow clinicians to identify potential drugs that could be used in those patients.”
Because most liquid biopsies are still in development, it’s difficult to predict exactly what this technology will do for medicine; however, MLPs are expecting to see many benefits arise alongside these new tests.
“A theoretical benefit will have to do with the indeterminate pulmonary nodules that are very common problems in medicine,” said Racke. “Frequently, those nodules have radiographic features that are worrisome for potentially being cancerous; however, they’re in locations where obtaining material poses significant risk to the patient in terms of morbidity from the procedural perspective. In those cases, it would be useful to have a plasma-based test that would inform on the likelihood of that nodule being malignant and increase the predictive value of a biopsy.”
Although the common use of liquid biopsies has yet to come to fruition, there’s no doubt that these tests will bring major changes to cancer diagnostics as a whole. “There is great hope and optimism — and desire to use these kinds of tests,” said Racke. “We see this as a really exciting field in cancer diagnostics.”
- National Cancer Institute.Blood test for genetic changes in tumors shows promise as alternative to tumor biopsy. Available at: https://www.cancer.gov/news-events/cancer-currents-blog/2016/asco-liquid-biopsy.