Liquid biopsies: A blood test for detecting and monitoring cancer?
We are living in an era where technological advances allow researchers to answer key questions relating to cancer biology in ways that they never could before. New and powerful approaches have opened doors particularly in the field of precision medicine; interventions that draw upon knowledge gained from biomedical research allowing for personalized therapies and treatment by understanding the underlying tumor biology). Liquid biopsies fall into this exact category and have recently become an area of intense research with anticipated extraordinary potential in cancer diagnosis, treatment monitoring, and surveillance.
As the term suggests, liquid biopsies are clinical samplings of bodily fluids, particularly blood. The rationale behind the use of liquid biopsies in the management of cancer comes from the following observation. The cells in our body are constantly being replaced and replenished. When a cell dies, it has the potential to release its genomic material (DNA) into the outside environment as part of a normal process. The DNA can then be “absorbed” into the blood circulation. We know that cancer cells in a tumor are also constantly dividing and dying. We also know that one fundamental difference between a normal cell and a cancer cell is that a cancer cell’s genetic material contains errors (or mutations). Therefore, the DNA that is released by dying tumor cells can be differentiated from that of normal cells when a blood sample is analyzed, we call this circulating tumor DNA (ctDNA). If we know what kind of DNA mutations a given tumor carries, then we can use this as a biomarker to pick up traces of a growing tumor in the body by characterizing ctDNA in the blood.
Breast, lung and colorectal cancers are cancer types that have gained decades worth of insight from research and clinical management. Many recent studies have assessed the use of ctDNA in these cancer types in monitoring how patients respond to treatment, where patients will relapse and tumor evolution.2 Other promising uses of ctDNA include monitoring for minimal residual disease and treatment resistance. Of the many benefits in the use of ctDNA, some notable points include the ease at which a liquid biopsy could be collected, allowing for the opportunity to follow changes and response in real-time and overcoming and, theoretically avoiding the need to perform invasive solid tissue biopsy collection.1 An observation of a normal phenomenon seen across all dying cells combined with our fundamental understanding of the characteristics of cancer cells has allowed us to leverage highly sensitive technologies in the advancement of cutting-edge cancer research. That being said, a lot of work still need to be done in standardizing methods of quantifying and analyzing ctDNA as there does seem to be large variations between patient-patient and between different types of cancers. Furthermore, through most applications of ctDNA have been across well studied cancer types, newly emerging studies aim to assess how ctDNA can be used for cancer types that are less prevalent.
Liquid biopsies as a whole can revolutionize the clinical management of cancer and offer additional hope for personalized care for patients in areas of early detection, diagnosis and disease monitoring.
This article was written by Sangeetha Paramathas. Sangeetha is currently a PhD candidate in the Department of Medical Biophysics at the University of Toronto. She studies how liquid biopsies can be used for cancer surveillance and diagnosis. To learn more about Sangeetha and her research, check out our members page.
References: Diaz LA Jr, Bardelli A. Liquidbiopsies: genotyping circulating tumor DNA. J Clin Oncol. 2014 Feb 20;32(6):579-86. Siravegna G, Marsoni S, Siena S, Bardelli A. Integratingliquid biopsies into the management of cancer. Nat Rev Clin Oncol. 2017 Mar 2. [Epub ahead of print]