Validation of a gene expression-based diagnostic system for malignancy of glioma by multi-institute prospective-retrospective analysis.

2066 Background: Histopathological classification of gliomas is often clinically inadequate due to the diversity of tumors that fall within the same class. Based on the strong correlation between malignancy and gene expression profile in gliomas, we constructed a diagnostic system based on gene expression profiling of 152 glioma samples (Shirahata et al., Cancer Sci, 2009, 100, 165). The diagnostic system was converted to that based on expression value of 27 genes measured with real-time PCR (Kawarazaki et al., BMC Med Genomics, 2010, 3, 52). Methods: First, the diagnostic system was validated with 75 retrospective samples from the National Cancer Center Hospital, and threshold values of the diagnostic score (PC1-score) were determined. Second, the system was evaluated by prospective-retrospective analysis of 127 samples from the four institutions using the threshold. The analysis corresponded to the category C proposed by Simon et al. (JNCI, 2010, 101, 1446). Results: In general, the PC1-score gradually ...