Liquid biopsy is a rapidly advancing field and the subject of intense interest from both academia and industry. Currently, there are growing numbers of companies involved in the development of liquid biopsy assays for the diagnosis and stratification of cancer patients. Because liquid biopsy can potentially provide a comprehensive, real-time assessment of the whole tumor burden for an individual patient, many experts believe it has the potential to replace the standard tissue biopsy. This is especially true for the following:
- To assess a patient’s tumor for early diagnosis
- To estimate the risk of metastatic relapse
- To stratify and perform real-time monitoring of therapies
- To identify therapeutic targets
- To determine resistance to therapy
The growth in liquid biopsy assays has certainly been assisted by the technological advances in next-generation sequencing (NGS), which allows for a faster and more comprehensive detection technique to understand the genetic makeup of a cancer.
Indeed, the development of new technology continues. Because of the very small amounts of tumor cells or tumor-specific DNA that exist in the blood, many biotechnology companies are developing special techniques to amplify and quantify cell-free, circulating tumor cells or tumor-specific DNA. For example, BioRad Laboratories of Hercules, CA has recently developed a Droplet Digital™ PCR (ddPCR™) technology to allow for highly sensitive and absolute quantification of nucleic acids associated with tumor DNA.
In the ddPCR™ method, nucleic acid samples from blood are partitioned into thousands of droplets using a water-oil emulsion system. Each droplet acts as a tiny, individual test chamber for nucleic acid amplification during PCR. Amplification occurs in all droplets simultaneously, and using fluorescence detection, the droplets are counted for target sequences providing for an absolute quantity of mutations.