Bile as a liquid biopsy matrix: potential applications and limitations

Hunting for tumoral material in body fluids, traditionally in blood, the so-called liquid biopsy is set to revolutionize the diagnosis and management of oncological patients. However, other biofluids can also be considered as alternative sources of biomarkers to provide clinically valuable information for multiple diseases. This is the case of bile, a fluid produced in the liver, stored in the gallbladder, and excreted to the duodenum, which complex composition is known to change in different pathological conditions. Remarkably, different works have demonstrated that the identification of mutations in bile cell-free DNA (cfDNA) can outperform blood analysis for the early diagnosis of biliopancreatic tumors causing biliary strictures. Here, the literature in which bile has been tested as a liquid biopsy matrix where lipids, metabolites, proteins, and cfDNA among other analytes were measured is reviewed. Moreover, the clinical situations and procedures where bile can be available, discussing the possible applications and limitations of bile analysis are summarized. The scientific relevance and clinical potential of bile harvesting, biobanking, and analysis are put forward. All this evidence supports the value of bile as a liquid biopsy matrix for the management of patients beyond cancer, and perhaps also beyond “blood, sweat, and tears”.