Personalized cancer medicine: present status and future perspectives

Most cancers have oncogenes and tumor suppressor genes. First successful drug targeting a oncogene is imatinib. It was very effective for chronic myelogenous leukemia as well as gastrointestinal stromal tumors. Many other targeted agents showed good response: trastuzumab for breast cancer, epidermal growth factor receptor tyrosine kinase inhibitors for non-small cell lung cancer, etc. Tests for EGFR and ALK gene mutation are routinely recommended for adenocarcinoma of lung cancer for selection of anticancer treatment. In addition, large-scale genomic data generation (next generation sequencing) is feasible in a clinical setting and gives us high hope for personalized cancer medicine. However, there are many hurdles to overcome. Driver genes must be distinguished from the passenger genes that are present in tumor DNA. In case of targeted cancer therapy, emergence of drug resistance due to tumor cell heterogeneity and clonal evolution is difficult to manage. Genetic testing for cancer risk showed some success in preventing familial breast or ovarian cancers, but it cannot be generalized in other tumors. Application of genetic information in cancer medicine showed promise but evidence-based approach is needed in clinical practice.