Liquid Biopsy
- Also Known As:
- Circulating Tumor Cell (CTC) Count
- Circulating Tumor DNA (ctDNA)

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At a Glance
Why Get Tested?
In very specific situations, these tests may provide additional information for your health practitioner, which could help determine prognosis or guide treatment for certain cancers, such as lung cancer and metastatic breast, colon, or prostate cancers.
When to Get Tested?
Your health practitioner will indicate whether this type of testing is medically appropriate and consider other options.
Sample Required?
A blood sample drawn from a vein
Test Preparation Needed?
No test preparation is typically needed. However, your health practitioner will tell you if you should alter any medications that you are taking prior to having your blood drawn.
What is being tested?
Researchers have known for some time that tumors shed cells and DNA or RNA into body fluids, including blood. In recent years, scientists have been able to gain information about tumors by analyzing these cells or DNA or RNA that circulate in the blood. These techniques require blood samples rather than the tumor tissue samples required by traditional biopsies, so they are often called liquid biopsies.
Tissue biopsies are the standard of care for cancer diagnosis. However, removing cancer tissue through surgery, or in some cases a needle biopsy, is an invasive process. In addition, the difficulty reaching a tumor can limit the ability of healthcare practitioners to sample it. However, the genetic information in tumor cells and tumor DNA or RNA may provide important information about the tumor, such as the likelihood of response to treatment, of relapse after treatment, or how the tumor is responding to cancer therapy. This has led to the emergence of liquid biopsy as a promising, non-invasive, complement to tissue biopsy.
By requiring a blood draw rather than a tissue biopsy, liquid biopsies can be more tolerable than traditional biopsies and may be acceptable for more frequent sampling to monitor cancer. As cancer treatments become more targeted to the genetic makeup of a tumor, liquid biopsies are a minimally-invasive way to understand how a tumor’s genetic make-up is evolving during treatment.
Currently, there are two main approaches to liquid biopsy:
- Circulating tumor cell (CTC) tests, which look at whole tumor cells in the blood
- Circulating tumor DNA (ctDNA) tests, which look for the DNA that tumor cells release into the blood
Other techniques, such as looking at cell fragments called extracellular vesicles (exosomes) or small molecules of non-coding RNA (microRNAs), are being studied.
In addition to applications such as cancer detection and treatment, liquid biopsies may also provide promise for cancer diagnosis, monitoring, and early detection. Currently, the medical applications of liquid biopsies are limited to determining prognosis in breast, colon, and prostate cancer, guiding treatment in those cancers, and guiding treatment of non-small cell lung cancer.
Common Questions
View Sources
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(2017 April 27). Patient Report Example, Circulating Tumor Cell Count, Breast Cancer. ARUP Laboratories. Available online at http://ltd.aruplab.com/Tests/DownloadReport/0093399%2C%20Abnormal%20Breast.pdf. Accessed June 2019.
NCI Staff. (2017 November 8). Liquid Biopsy: Using DNA in Blood to Detect, Track, and Treat Cancer. National Cancer Institute. Available online at https://www.cancer.gov/news-events/cancer-currents-blog/2017/liquid-biopsy-detects-treats-cancer. Accessed June 2019.
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Liquid Biopsy Test Shows Promise for Detecting Early-Stage Colorectal Cancer. American Society of Clinical Oncology. Available online at https://www.asco.org/about-asco/press-center/news-releases/liquid-biopsy-test-shows-promise-detecting-early-stage. Accessed June 2019.
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