ddPCR Provides the Level of Sensitivity Required for Liquid Biopsy
ddPCR is a powerful technology that provides absolute quantification of nucleic acids with a high degree of sensitivity and precision. For more detailed information on the technique, see the ddPCR technology page and the QX200™ Droplet Digital™ PCR System product page. In blood, the cfDNA, ctDNA, and CTCs of interest are present at low levels and found in a complex background of other components. Additionally, circulating DNA is highly fragmented, which further reduces the concentration of intact target sequence. The recent advent of more sensitive screening techniques, such as ddPCR, has permitted the detection and quantification of low abundance targets in shorter times without requiring large numbers of replicates. This has established ddPCR as a tool of choice for liquid biopsies.
Use of Liquid Biopsy for Cancer Diagnosis and Monitoring
One area of active research and development for liquid biopsy is the field of oncology. Cancer provides some unique challenges for detection and monitoring because of the number of genotype changes involved and tumor heterogeneity. Liquid biopsy is minimally intrusive compared with other methods, such as solid tissue biopsy. Samples of blood, sputum, and other fluids can be collected without the significant risk of causing harm when trying to reach affected organs that are difficult to access. Liquid biopsy also facilitates the following:
- Monitor and determine treatment protocols — liquid biopsies can monitor effectiveness of a treatment protocol, optimize a regimen, determine whether changes in treatment regimen are beneficial, and detect if a treatment protocol loses its efficacy
- Follow any changes in a tumor — many tumors change over time; the ability to monitor changes can provide information for changes in treatment
- Screen for reoccurrence — screening patients in remission can detect new tumor growth before physical signs are apparent, whether a tumor is in the same location or has metastasized
- Routinely screen for high risk patients — in cases where certain genotypes have been identified in individuals, liquid biopsies can provide early detection of cancer before there are any overt symptoms or until the cancer is detectable by conventional imaging
The use of liquid biopsy is rapidly revolutionizing the detection and monitoring of cancer and an increasing number of diseases. The ability to detect a disease prior to the appearance of symptoms and start treatment at an early stage can reduce or slow damage and improve quality of life. Furthermore, monitoring during treatment will permit optimization of disease management at the individual level, providing effective treatment while minimizing side effects.
The unmatched sensitivity of ddPCR for detecting low abundance targets in complex backgrounds will play a major role in the use of liquid biopsies. This technology provides fast detection and accurate quantification of disease markers and accomplishes this with a minimal amount of discomfort for the patients.
