Limitations of Liquid Biopsy
- Liquid biopsy is an innovative new technology that tests cancer cells circulating in your bloodstream.
- It is not as sensitive a test as tumor-based next-generation sequencing (NGS) but it can be faster and easier.
- The test should be used together with tumor-based next-generation sequencing.
- A repeat tumor-based test or a liquid biopsy may be considered if resistance to a targeted therapy appears to develop.
Dr. Valsamo Anagnostou, a thoracic oncologist and leader of the Johns Hopkins Molecular Tumor Board at The Sidney Kimmel Comprehensive Cancer Center explains why liquid biopsies are so “exciting” in the field of oncology:
Read MoreLimitations of Liquid Biopsy
Currently, liquid biopsy is not a standard method for early diagnosis or detection of cancer or its mutations and alterations. Liquid biopsy looks for very small pieces of tumor DNA and circulating cells in the blood which can be difficult to detect, as opposed to a tissue biopsy which often takes a piece of a known tumor or mass. For that reason, there is a higher chance the liquid biopsy misses the diagnosis.“Because these technologies are now emerging and there are sensitivity issues, there is a higher chance for a false-negative result. So that is the reason the liquid biopsies are used as an adjunct to next-generation sequencing tumor tissue, especially when the tumor is not sufficient for testing,” Dr. Anagnostou explains.
A false-negative result occurs when any test incorrectly determines a negative result, meaning the test is actually positive. In this situation, that would mean that although there is cancer, the liquid biopsy did not detect evidence of circulating tumor DNA (ctDNA) or tumor cells in the blood (CTCs). Because of this, liquid biopsy is often used as a supplement to tissue biopsy and is typically considered when there is not enough tumor available for testing or when unable to undergo further tissue biopsies.
Reasons for Getting a Repeat Biopsy
Due to the possibility of false-negative results, it is important to do a liquid biopsy together with tumor-based next-generation sequencing. That is one reason repeat next-generation sequencing or a repeat liquid biopsy might be helpful. According to Dr. Anagnostou, there is another reason it might be worth considering:
“The other scenario where a repeat biopsy be it a tissue biopsy or liquid biopsy may be informative is when we’re trying to capture a mechanism of resistance to therapy and do something about it.”
Resistance to certain targeted therapies can emerge over time. A repeat tumor biopsy or liquid biopsy can help your oncologist understand how the genetic makeup of your cancer cells has changed and what is causing that resistance at a DNA level.
“And whether there is any new target that has emerged that we can target with a different targeted therapy,” Dr. Anagnostou explains.
Questions to Ask Your Doctor
- Should a liquid biopsy be considered as part of my molecular testing?
- Has a liquid biopsy been done together with my tumor-based molecular testing?
- Are false-negative results a possibility? And if so, how should we address them?
- Is there any reason to repeat my tumor biopsy or liquid biopsy?
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