Abstract 5450:CYP2A6andERCC1polymorphisms correlate with efficacy of S-1 plus cisplatin in metastatic gastric cancer patients

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Introduction: S-1 contains tegafur, which is converted to 5-fluorouracil by CYP2A6. We evaluated the association between polymorphisms of CYP2A6, ERCC1 and XRCC1 and treatment outcomes of metastatic gastric cancer (MGC) patients treated with S-1/cisplatin. Methods: Among chemonaive MGC patients (n=108) who received S-1 40 mg/m2 b.i.d. on days 1-14 and cisplatin 60 mg/m2 on day 1 of a 3-week cycle, we analyzed the wild-type allele \[W\] (CYP2A6*1), four CYP2A6 variants [V] that abolish (CYP2A6*4) or reduce (CYP2A6*7, *9, *10) enzyme activity, and the polymorphisms of ERCC1 [8525C>T (rs11615), 19442C>A (rs3212986)] and XRCC1 [1196G>A (rs25487)]. Results: Patients having fewer CYP2A6 variants had significantly better response rates (W/W vs W/V other than \*1/\*4 vs V/V or \*1/\*4 = 66.7% vs 58.3% vs 32.3%; P=0.008), time to progression (TTP) (median, 7.2 vs 6.1 vs 3.5 months, P=0.021), and overall survival (median, 23.2 vs 15.4 vs 12.0 months, P=0.004). ERCC1 19442C>A was also associated with response rate (C/C, 46.7% vs C/A, 55.3% vs A/A, 87.5%) (P=0.048) and TTP (median, 4.4 vs 7.6 vs 7.9 months) (P=0.012). When we classified patients according to the number of risk genotypes of CYP2A6 (V/V or 1/*4) and ERCC1 19442C>A (C/C), patients carrying two vs those carrying none showed an adjusted odds ratio of 0.113 (95% CI, 0.025-0.509) (P=0.004) for response and adjusted hazard ratios of 3.748 (95% CI, 1.900-7.393) (P=0.0001) for TTP and 2.961 (95% CI, 1.371-6.393) (P=0.006) for death.Conclusion: CYP2A6 and ERCC1 19442C>A polymorphisms are important predictors for the efficacy of S-1/cisplatin in MGC patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5450. doi:10.1158/1538-7445.AM2011-5450