Practical issues of biomarker-assisted targeted therapy in precision medicine and immuno-oncology era

The concept of precision medicine is not new, as multiplex and very sensitive methods, or next-generation sequencing and matched targeted cancer therapies, have come to clinical practice. Substantial progress has been made from the discovery to the development and clinical application of biomarkers and matched targeted therapies. However, there still remain many challenges and issues to be overcome in each step, from acquisition of tumour tissues through validation of biomarkers to the final decision on targeted therapy. This review will briefly touch on these issues, hoping to provide a better understanding and application of targeted therapy in cancer treatment in the era of precision medicine and immuno-oncology. It also helps to understand that the meaning or value of biomarker(s) and matched targeted therapy changes along with expansion of knowledge and advance of methodology, and constant efforts have to be made in evaluating the meaning and clinical value during the development and after the establishment of biomarkers or the approval of matched targeted therapies, which might be more complicated by the advent of new therapeutic agents and new diagnostic methods.