External validation of a tumor-derived 5-gene prognostic signature for recurrence (R) of stages I/II colon and stage I rectal cancer following potentially curative resection.

437 Background: Optimizing post-operative clinical management for early-stage (I/II) colorectal cancer (CRC) patients (pts) is a significant unmet medical need. We hypothesized that a molecular prognostic test using primary CRC tissue would better predict the chances of tumor R within 36 months (mo) than current NCCN Clinical Practice Guidelines (NCCN). Methods: Pts had tumor R by 36 mo (n=46) or confirmed non-recurrence (NR) for ≥36 mo (n=69) after surgery; none had received neoadjuvant or adjuvant therapy. Archival formalin-fixed paraffin-embedded primary adenocarcinoma tissues (median storage 7 years; range 4-15) obtained at initial surgical resection with curative intent were retrieved for 86 stage I/II (pT1-4 pN0 M0) colon cancer and 29 stage I (pT1-2, pN0 M0) rectal cancer pts from 2 US and 2 European sites that were different from those previously used to generate the molecular test. Tumor gene expression was assessed by qRT-PCR with custom 384- well TaqMan Low Density Arrays (Applied Biosystems) u...