Phase II: A Simon's optimal two-stage phase II study will be conducted in patients with unresectable locally advanced or metastatic gastric or gastro-esophageal cancer at the RPTD of the ECC regimen. A total sample size of 43 patients will be required, 13 in the first stage and 30 in the second stage, if criteria for second stage accrual are met. If <=3/13 patients respond, this is deemed to correspond with the initial rejection limit and no further patients will be enrolled. If >=4/13 patients respond, an additional 30 patients will be enrolled in the second stage (total sample size = 43). Further statistical details are specifically outlined in Section 8 of the protocol. The response rate, standard error and its 95% confidence intervals (CI) will be calculated under the binomial distribution model. The efficacy of the regimen will then be evaluated by comparing the point estimates and 95% CI with historical data. Potential covariates for response will also be identified and evaluated via the logistic regression model. Kaplan-Meier estimates will be computed to estimate the secondary endpoints such as time to progression and survival. Cox-regression model can be applied incorporating covariates in the model. Fisher's exact test will be applied to compare the response rates between the different genetic TS polymorphisms groupings.