Genomic profiling of muscle invasive bladder cancer to predict response to bladder-sparing trimodality therapy.

513Background: Trimodality therapy with TURBT followed by chemoradiation is an acceptable alternative to cystectomy for muscle invasive bladder cancer (MIBC). Genomic profiling has demonstrated MIBC can be divided into molecular subtypes with differing responses to chemotherapy. We explored the utility of genomic data to select patients for bladder-sparing trimodality therapy. Methods: Transcriptome wide gene expression profiles were generated for 189 MIBC TURBT samples from patients treated with trimodality therapy at a single institution. Of these, 103 passed microarray QC. Molecular subtype and expression of bladder cancer genes were assessed for association with overall and disease-specific survival. Transcriptome wide differential expression analysis was used to explore gene set enrichment in trimodality therapy response groups. Results: The chemoradiation cohort (n = 103) had a median followup of 6.9 years for alive patients, and was classified into four subtypes: basal (n = 44), basal claudin-low (...