Use of gene set analysis (GSA) for molecular classification of responders and nonresponders to FOLFOX therapy in colorectal cancer (CRC).

3628 Background: Folinic acid (FOL) fluorouracil (F) and oxaliplatin (OX) chemotherapy is a commonly used therapy for CRC. Lacking in current literature are clinically relevant classifiers for potential responders. GSA technique is statistical method that detects significance of sets of genes, instead of examining a gene-by-gene basis. The objective of this study was to identify differential functionally annotated gene expression profiles associated with response to FOLFOX therapy in CRC tumors using gene-by-gene and GSA approaches. Methods: Genome wide expression profile data were collected on pre-treatment tumor tissues from patients with unresectable CRC receiving FOLFOX therapy (n = 83, Affymetrix HG U133A, GSE28702, Tsuji et al. BJC 2012). Gene expression was compared between responders (n = 42) and Non-responders (n = 41). GSA was conducted on 3272 curated gene sets from the Molecular Signatures Database (Subramanian, Tamayo et al. 2005, PNAS 102, 15545-15550) annotated by biological pathway, bioche...