Liquid Biopsies Will Drive Treatment Decisions in the Future

Doctors and patients both want to know when cancer is present in the patient’s body. Imaging is helpful in this respect because it can identify masses that should not be there. But imaging is far from perfect. It can confuse benign lesions for malignant ones, it lacks the ability to determine important histological features that impact prognosis or treatment, and it is insensitive to both small lesions and lesions outside of the anatomic field scanned. Molecular imaging that uses radioligands targeted to specific molecules expressed by cancer cells (eg, prostate-specific membrane antigen or fluorodeoxyglucose positron emission tomography) is better than anatomic imaging at detecting tumors in many types of cancer. Still, this form of imaging lacks sensitivity, can have false-positive findings, and does not provide enough molecular information to confirm a specific histologic diagnosis or guide treatment decisions. Biopsy, both surgical and imaging-guided, can be used to pathologically characterize tumors large enough to be seen on imaging but is significantly limited by cost, morbidity, tumor size, and tumor location. How then can we detect and treat cancer before it is too large and widespread to cure? This is where liquid biopsies come into play, at least in theory.