Personalized medicine with germline pathogenic variants: Importance of population‐ and region‐wide evidence

Rare germline pathogenic variants in cancer‐predisposing genes have a high impact and potential for clinical utility. In the last 30 years, based on evidence of cancer risk associated with germline pathogenic variants, several measures have been suggested for personalized medicine, including the development of novel treatments, treatment stratification, risk reduction by surgical measures, chemoprevention, removal of environmental factors, and surveillance for early detection among specific high‐risk individuals. However, this evidence is mainly based on evaluations of European populations. Our large‐scale analyses of more than 100,000 individuals, including 14 disease cases and non‐cancer controls in the Japanese population, suggest some discrepancies in the associations between cancer‐predisposing genes and diseases, expansion of the targeted diseases of BRCA1 and BRCA2, and a potential novel risk‐reduction measure for gastric cancer. They are likely to be explained by population and region variations; therefore, more population‐wide and region‐wide research could provide improved personalized medicine as well as a better understanding of disease mechanisms. This review summarizes current personalized medicine and discusses the potential use of germline pathogenic variants.