Introduction
Using imaging and guided procedures is important for checking, diagnosing, and surveilling cancer. Although the newer imaging methods are more precise and help understand tumors better at a molecular level, profiling tumors for targeted therapy mostly needs getting tissue directly. But even with targeted therapy, tumors can become resistant, so there is an ongoing need to keep monitoring them, usually by taking tissue samples to identify the reason behind tumor resistance and to plan treatment. Instead of using tissue sampling, now one can also do a liquid biopsy, where tumor markers are collected from the blood. This method is less invasive and shows potential for cancer detection and monitoring.
What Is a Liquid Biopsy?
Liquid biopsy is a non-invasive tool for cancer detection. It includes a collection of circulating tumor markers like circulating tumor cells and cell-free nucleic acids from the blood samples. Within the tumor environment, the cancer cells release biomarkers into the bloodstream, which can be gathered together and studied to understand tumor biology. In recent days, liquid biopsy has been utilized in clinical practice when tissue sampling is not accessible or when the sample obtained is insufficient. Additionally, researchers are studying its utility in cancer screening, diagnosis, and surveillance. As cancer care increasingly highlights precision medicine, the emergence of the latest liquid biopsy technology can influence the role of imaging in cancer management.
How Does Liquid Biopsy Help in Cancer Diagnosis?
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Both growing and apoptotic cancer cells will release specific biomarkers into the bloodstream, which can then be captured in a venous blood sample.
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Among these biomarkers, circulating tumor DNA (ctDNA) and circulating tumor cells (CTCs) have been elaborately studied.
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Studying these tumor biomarkers helps physicians offer a largely noninvasive approach for screening, diagnosing, prognosis, and guiding therapy for various types of cancers.
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It is also important to keep in mind that while liquid biopsy involves puncturing a peripheral vein with a needle, it is generally considered non-invasive, similar to diagnostic imaging that requires intravenous contrast.
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Liquid biopsy includes collecting blood from a peripheral venous site such as the median cubital vein. These tests generally require only a small amount of blood.
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Additionally, other promising biomarkers include microRNA, tumor-derived exosomes, and tumor-educated platelets.
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Although they are still in their early stages of development, they are helpful in diagnosis. It is also notable that some biomarkers, such as ctDNA, microRNA, and tumor-derived exosomes, are also detected in bodily fluids, excluding blood.
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These fluids include saliva, urine, pleural fluid, and cerebral spinal fluid (CSF). This broader range of sample sources improves the potential for noninvasive diagnostic approaches across various bodily fluids.
What Is the Significance of Liquid Biopsy in Cancer Management?
Radiologists play an important role in cancer treatment. For instance, interventional radiologists will perform minimally invasive local-regional therapies, and nuclear medicine physicians will administer radionuclide therapy. Traditionally, tumor characterization through imaging has been focusing on enhancement characteristics and metabolism. However, advancements in molecular imaging have paved the way for deeper tumor characterization, which thus helps in treatment selection, dose determination, and acquiring data on tumor metabolism through techniques like nuclear medicine and MR spectroscopy.
As technology advances, the expenses for medical tests decrease. Liquid biopsy could complement medical imaging in diagnosing and staging cancer. Liquid biopsy can provide similar tumor information to percutaneous biopsy. This minimizes the risks associated with invasive procedures and reduces the overall need for such biopsies. Radiologists tend to find new roles in using this liquid biopsy technology for selecting treatment protocols and managing patients undergoing local-regional therapies for cancer. This can also involve monitoring treatment efficiency and guiding post-procedural care.
What Is the Scope of Liquid Biopsy in Cancer Management?
As liquid biopsy technology progresses, the role of imaging in cancer diagnosis and post-treatment monitoring will progress accordingly. With much-improved technology and reduced costs, liquid biopsy can reserve a special place as a highly sensitive and specific tool for diagnosing and treating cancer in the near future. The foundation of screening protocols for certain cancers in specific patient groups will lead to effective and easier cancer detection.
Early clinical research has suggested that liquid biopsy is able to identify molecular residual disease and detect disease before it is visible on imaging scans. It is also possible that patients with early-stage cancer could be monitored after surgery or local-regional therapy using liquid biopsy to check for any residual disease before it is detected through imaging techniques. Large-scale clinical trials are necessary to find out if regular imaging surveillance can be replaced with liquid biopsy diagnostic monitoring for patients who show no signs of molecular residual disease. On the other hand, patients who have evident molecular residual disease will require more advanced imaging techniques, such as PET/CT scans, to increase sensitivity in identifying any remaining or metastasizing cancer.
What Is the Downside of Liquid Biopsy?
The use of imaging tests like CT (computed tomography) scans and MRI (magnetic resonance imaging) can help detect the exact precise location of a tumor. While the use of imaging for diagnostic purposes, such as low-dose CT scans for lung cancer, may decrease, diagnostic imaging for pinpointing the exact location of disease will likely remain steady or even increase. Though liquid biopsy helps in providing information about the presence and mutation of the cancer, it cannot detail the anatomical staging, which is an important factor in analyzing the prognosis. So, imaging will still continue to play a crucial role in anatomical staging and treatment planning. Meanwhile, liquid biopsy will complement these by aiding in more precise treatment selection based on tumor mutation status and facilitating earlier cancer detection through screening protocols.
Conclusion
Liquid biopsy is a novel diagnostic tool that is non-invasive. It also helps in detecting residual cancer before it is evident in diagnostic scans that are commonly used for cancer detection. These innovations, with the integration of artificial intelligence and the emergence of fields such as theranostics ( a combination of therapeutics and diagnostics) and radionics (an artificial intelligence tool used for cancer analysis), and the coordination and expertise of radiologists together contribute to enhancing patient care in cancer treatment.
