Validation and genomic interrogation of the MET variant rs11762213 as a predictor of adverse outcomes in clear cell renal cell carcinoma

395 Background: The exonic single nucleotide variant rs11762213 located in the METoncogene has recently been identified as a prognostic marker in clear cell renal cell carcinoma (ccRCC) (Schutz et al, Lancet Oncol 2013). We sought to validate this finding and explore the biologic implications using The Cancer Genome Atlas (TCGA) cohort. Methods: The variant call file (VCF) and expression data was available for 272 patients. We then extracted the data for rs11762213 as follows for the "normal" sample: allelic fraction for variant allele > 80% is homozygous variant while allelic fraction for variant allele 30% to 70% is heterozygous. Paired tumor-normal materials, genomic data (whole exome, RNAseq, and DNA methylation) and clinical information were acquired from publically available TCGA datasets. Kaplan-Meier method was used to estimate the survival probabilities. Cancer specific survival (CSS) was analyzed using the competing risk method and Cox proportional hazard regression was used for analysis of time to recurrence. Multivariate competing risk models were also fitted in the TCGA cohort in order to adjust for the Mayo Clinic SSIGN score. Results: Overall, the variant allele of rs11762213 was detected in 10.3% of the cohort and was associated with higher nuclear grade (p=0.03) and trended toward higher clinical stage (p=0.07). After adjusting for the prognostic SSIGN score, the risk allele remained a significant predictor for adverse cancer specific survival (CSS; p