Abstract 4672: Tumor dihydropyrimide dehydrogenase (DPYD) expression is associated with survival in patients with metastatic colorectal cancer treated with gefitinib, 5-fluorouracil, leucovorin, and oxaliplatin (IFOX)

New drugs that target the EGFR signaling pathways suggest that EGFR inhibition exerts a chemosensitizing effect in colorectal cancer. We have previously reported that the combination of gefitinib, leucovorin, 5-flourouracil, and oxaliplatin (IFOX) resulted in higher response rates than those reported with FOLFOX-4 alone in patients with metastatic colorectal cancer. The aim of the present study was to examine genomic factors that might be associated with response or survival in the IFOX regimen. Patients and Methods: Seventy-two patients had stage IV colorectal adenocarcinoma and were either untreated or previously treated prior to receiving the IFOX regimen. Formalin-fixed, paraffin-embedded tissues (FFPE; n=63) were obtained, and 4-um sections were cut, placed on slides, and deparaffinized in xylene, followed by laser capture microdissection (LCM; n=42) to enrich for tumor cells. Using real-time quantitative RT-PCR, thirty-five samples had good-quality actin RNA readings following LCM, and the expression levels of dihydropyrimidine dehydrogenase (DPYD), epidermal growth factor receptor (EGFR), excision repair cross-complementing rodent repair deficiency complementation group 1 (ERCC1), thymidylate synthase (TYMS), and thymidine phosphorylase (TYMP) were separately quantified. To detect mutations in KRAS, DNA was extracted from fifty-eight patient samples and analyzed using the KRAS Mutector II kit (TrimGen, Sparks, MD). Results: For the 33 patients available for RT-PCR analysis, expression levels of DPYD, EGFR, ERCC1, TYMP, or TYMS did not correlate significantly with response. However, in terms of survival, the overall survival rate was significantly worse in patients with a high DPYD expression level compared to patients with a low DPYD expression level (p