Molecular determinants of capecitabine efficacy in colorectal cancer

3606 Background: Capecitabine offers physicians a more convenient treatment for advanced colorectal cancer (CRC), with manageable toxicity and antitumor activity comparable to that of continuous-infusion therapies with 5-fluorouracil (5-FU). However, there are no validated and established predictive factors for clinical outcome of capecitabine efficacy in CRC. Therefore we investigated whether intratumoral mRNA expression levels of genes involved in the capecitabine/5-FU metabolism (cytidine deaminase (CDA), dihydropyrimidine dehydrogenase (DPD), folylpolyglutamate synthase (FPGS), gamma-glutamyl hydrolase (GGH), thymidine phosphorylase (TP), thymidylate synthase (TS)) and in angiogenesis (cyclooxygenase 2 (Cox-2), epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF)) are associated with the clinical outcome of patients with metastatic CRC treated with first-line capecitabine. Methods: Thirty-seven patients with metastatic CRC were enrolled in this study and treated with single agent capecitabine.The intratumoral mRNA levels of CDA, COX-2, DPD, EGFR, FPGS; GGH, TP, TS, and VEGF were assessed from paraffin-embedded tissue samples using laser-capture-microdissection methods and quantitative real-time PCR. Results: There were20 women and 17 men with a median age of 61 years (range 49–74). The median progression-free survival was 6.7 months (95% CI, 4.8–11.6 months), with a median follow up of 14.4 months (range: 1.3 to 18.7 months). Complete response was observed in 1 (3%), partial response in 6 (20%), stable disease in 14 (47%) and progressive disease in 9 (30%) patients (response was inevaluable in 7 patients). Higher gene expression levels of DPD were associated with resistance to capecitabine (P= 0.032; Kruskal-Wallis test). Patients with a lower mRNA amount of DPD (≤0.46) had a longer progression-free survival compared with patients that had a higher mRNA amount (8.0 vs. 3.3 months; adjusted P=0.048; log-rank test). Conclusions: This pilot study suggests that intratumoral gene expression levels of DPD may be useful to predict the clinical outcome of patients with metastatic CRC with first-line single agent capecitabine treatment. Our data are hypothesis generating and should be validated in larger and prospective clinical trials. [Table: see text]