Liquid biopsies: potential game changer in oncology
In cancer, tissue biopsy is still the gold standard that holds the final diagnosis. Removing tissue from a tumor often involves a painful procedure with a needle leading to much discomfort among patients. Modern oncological research has recently ideated liquid biopsy, a process by which diagnosing and monitoring cancer can be done non-invasively, that is, by a simple blood test that can locate DNA fragments from the cancer, with the least discomfort for a patient of any age.
With this new technique, a tumor’s specific mutation can be diagnosed by the tumor DNA circulating in the blood. Although liquid biopsies are not currently used to diagnose cancer, disease progression and detecting genetic mutations in the tumor is possible that could suggest which drug should be used to treat the disease, as well as predicting response to therapy. Research in this new frontier is still ongoing.
From the available data, blood from patients with breast, colorectal, and lung cancers have shown similar mutations compared to tissue biopsy results. This might be encouraging, but for about 15% of patients, DNA might just be absent in the blood. Early detection of cancer is a key area in all cancer research and nobody wants to miss an early diagnosis of cancer that might just be curable or treatable.
Other than the simple, non-invasive blood test, liquid biopsies include samples from urine and the cerebrospinal fluid. Tapping cerebrospinal fluid is important in tumors of the brain and although the procedure can be painful, but is far less invasive compared to the traditionally required risky procedure of obtaining brain tumor tissue samples. The cerebrospinal fluid bathes the brain and spinal cord and is in direct contact with the brain tumor cells providing vital information regarding the type and staging of the tumor. Urine allows for much more volume than a blood sample. In addition, urine samples can be collected every day.
Then, there is the issue of cost. Liquid biopsies have the advantage of being cost-effective as opposed to traditional biopsy methods, for example, brain surgery versus a cerebrospinal tap. Or a blood test in colorectal cancer versus the discomfort and risks associated with colonoscopy.
Cancer is a complex and dynamic disease that has the capacity to change over time and behave differently in different individuals. The development of reliable and robust non-invasive platforms for the diagnosis, patient stratification and to monitor treatment response is necessary for each individual. The various liquid biopsy platforms currently available have the potential to add tremendous value to the care of cancer patients. It is hoped that the next frontier will be for liquid biopsies to detect all types of cancer, even at the early stages, provide early warning for disease recurrence, and overcome false positives and false negatives of the results.
Although liquid biopsy is used quite frequently for the treatment and follow up of leukaemias (blood cancer); a large number of solid tumours need to be validated against biopsy specimens before we can definitely adopt liquid biopsies for all sites as the gold standard.