Abstract
9652 Background X (Xeloda®) is a tumor-activated oral fluoropyrimidine, with superior response rate and improved safety compared to bolus 5-FU/LV in 1st-line MCRC. Variation in tumor expression levels of thymidine phosphorylase (TP), thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) may impact efficacy or toxicity of X-containing regimen. We are retrospectively evaluating the relationship of the expression of these enzymes to outcomes in a 1st-line MCRC phase III trial of X vs 5-FU/LV (Hoff, JCO 2001). 9 Canadian sites participated in the trial (N=164). Methods Pts were eligible if they received at least one dose of chemotherapy. We obtained informed consent through next-of-kin or Ethics Committee waiver. We obtained formalin-fixed, paraffin-embedded tissue from primary tumors +/- synchronous metastases. We analyzed TP, DPD and TS expression levels using immunohistochemistry (IHC) and quantitative reverse transcriptase - polymerase chain reaction (RT-PCR) kits, both from Roche Diagnostics. Overall IHC score was calculated using tumor and stromal staining intensity and pattern. IHC intensity and percentage of staining were scored blinded to pt treatment and clinical outcome.Results Tumor blocks from 37/164 pts have been analyzed to date, 34 primaries (see table), 4 metastases (not shown). Data on correlation of IHC and RT-PCR results to clinical outcomes will be presented at the meeting. Conclusions Retrospective sample collection was feasible in a large multicenter trial. Sophisticated molecular analysis of archival samples was performed with a success rate of 97%. Results of this biomarker analysis could generate a hypothesis to be tested in further prospective research with X, eventually allowing tailored therapy for the individual patient. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Hoffmann-La Roche Hoffmann-La Roche Hoffmann-La Roche
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