Unleashing the potential of liquid biopsy in solid tumors: diagnosis, recurrence and resistance

Despite advances in screening and therapeutics cancer continues to be one of the major causes of morbidity and mortality worldwide. Tumor molecular characterization plays a key role in choosing the right treatment among the armamentarium available to the oncologist. The molecular profile of tumor is routinely assessed by surgical or bioptic samples, however, genotyping of tissue has inherent limitations: it represents a single snapshot in time and it is subjected to spatial selection bias owing to tumor heterogeneity. Liquid biopsy has emerged as a novel, non-invasive opportunity of detecting and monitoring cancer in several body fluids instead of tumor tissue. Circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), RNA (mRNA and micro-RNA), microvesicles, including exosomes and tumor “educated platelets” were recently identified as a source of genomic information in cancer patients which could reflect all subclones present in primary and metastatic lesions allowing sequential monitoring of disease evolution. To date, liquid biopsy has been successfully used in patients affected by melanoma, breast, colorectal, and lung cancer as reviewed above. Thus, it is reasonable to suppose that, once methodological procedures will be standardized and harmonized across laboratories, liquid biopsy-based evaluations will be even more used in routine settings for diagnosis and treatment of cancer patients.