BJRD151030 1..17

Recently, radiogenomics or imaging genomics has emerged as a novel high-throughput method of associating imaging features with genomic data. Radiogenomics has the potential to provide comprehensive intratumour, intertumour and peritumour information non-invasively. This review article summarizes the current state of radiogenomic research in tumour characterization, discusses some of its limitations and promises and projects its future directions. Semiradiogenomic studies that relate specific gene expressions to imaging features will also be briefly reviewed. INTRODUCTION In recent years, a new direction in cancer research has emerged to address high-throughput methods of associating imaging features with genomic data. This approach is referred to as radiogenomics or imaging genomics. The imaging characteristics of a disease are also called its imaging phenotype or radiophenotype, while the genomic information defines the molecular phenotype or genotype of the disease. Research to uncover the underlying genetic causes of individual variation in sensitivity to radiation using high-throughput genomic methods has also been referred to as “radiogenomics” and is not discussed in this review. Much of the discussion of personalized medicine has focused on molecular characterization using genomic and proteomic technologies. However, a limitation of these approaches is the need to acquire tissue samples through invasive surgery or biopsy. Although some genetic analyses have been incorporated into clinical practice in recent years, large-scale genome-based cancer characterization is not routinely performed owing to its cost, turnaround time and technical complexity required for data analysis and interpretation. In addition, samples are often obtained from a small portion of a heterogeneous lesion and may not accurately represent the lesion’s anatomic, functional and physiologic properties. Even more importantly, it is not feasible to obtain the tissue multiple times during treatment in order to monitor response. Consequently, it is still a challenge to incorporate genomics or proteomics into routine clinical practice. Imaging has great potential for in vivo tumour characterization because it can provide a more comprehensive view of the entire tumour than biopsy samples alone. For example, imaging can provide information on peritumoral regions, which are typically not surgically removed and thus not analysed in the laboratory. Human tissues often exhibit a diversity of distinctive traits on radiographic images, many of which currently have no known clinical significance. Furthermore, routine clinical practice often includes followup imaging to monitor treatment response and disease progression. Advances in imaging technologies now provide better anatomic localization and allow for non-invasive measurements of functional and physiologic tissueand lesion-specific properties. Potentially, one would benefit tremendously from radiogenomic biomarkers that measure gene expression at frequent intervals during therapy. Oncologic diagnosis is quickly moving from the traditional histology-based approaches to molecular stratification. Therefore, the traditional radiology–pathology paradigm alone is no longer sufficient to radiologists. Radiogenomics T a b le 1. R a d io g e n o m ic st u d ie s p u b lis h e d in th e lit e ra tu re St u dy Y ea r C ou n tr y D at a so u rc e N u m be r V al id at io n se t C an ce r Im ag in g m od al it y N u m be r of fe at u re s M et ho d of