Liquid biopsy: A liquid biopsy is blood test that detects tumor DNA that are freely circulating in the blood when cancerous tumor cells die. Elevated levels of these freely circulating tumor cells can be identified in the peripheral blood of the patient as compared to healthy individuals. Its is a non invasive biopsy, in that, it only requires a sample of blood drawn with a syringe instead of the conventional core biopsy which often requires surgery.
The quantity of free circulating DNA has been shown to correlate with tumor burden and determine tumor heterogeneity.
Advantages of Liquid biopsy
It is quicker, easier and less painful.
It is less traumatic for the patient compared to surgical biopsy.
Since it involves drawing blood, it can be repeated multiple times as and when needed.
It helps in early detection of cancer.
It helps to determine whether the patient is responding to the current treatment protocol.
It helps predict the chances of recurrence.
It helps identify treatment resistance.
Role of Liquid biopsy colorectal cancer.
Colorectal cancers (CRC) usually have wide heterogeneity with general genomic instability. Liquid biopsy in CRC helps in analysing circulating tumor cells (CTCs) and genomic material including cell-free DNA (cf DNA) which acts as a complementary tool to solid tumor tissue.
Liquid biopsy detect mutated DNA in the blood and compare then with DNA mutations measured in primary tumor obtained during initial surgery.
It helps measure amount of markers in the blood which could help detect residual disease after surgery, measure response to treatment, disease progression, etc.
Liquid biopsy helps determine tumor genotype to better design treatment effective for the patient. For eg., if the liquid biopsy indicates that a patient responded well to the early chemotherapy, there is a possibility that surgery could potentially cure the disease. But if they did not respond well, its likely the cancer is too widespread and cant be eradicated with surgery and so those patients should receive more chemotherapy to control their disease.
Studies suggest that residual disease detected in liquid biopsies was predictive of outcomes. In addition, it can potentially help identify patient who would be candidates for targeted therapy and immunotherapy, etc.
A new study from Washington School of Medicine in St. Louis, demonstrates that a liquid biopsy examining blood or urine can help gauge the effectiveness of therapy for CRC that has just begun to spread beyond the original tumor.
The study appears online in the Journal of Clinical Oncology Precision Oncology, a journal of the American Society of Clinical Oncology.
Although Liquid biopsy is still in nascent stage, and core biopsy and colonoscopy still remains the gold standard in CRC, several ongoing studies and more and more approvals are in the pipeline and pretty soon, liquid biopsy may have the potential to become a primary diagnostic tool in detecting early stage CRC, determine first, second -and third line treatment based on circulating tumor DNA and offer non invasive and cheaper alternative to surgical biopsy.