Personalized Therapy for Esophagogastric Cancer Using Thymidylate Synthase Genetic Markers

In this study the investigators aim to: 1) confirm the objective response rate (ORR) observed in the investigators initial study for patients with the TSER\*2/\*2 genotype 2) determine whether PEMOX regimen is more worthy of future development for this patient genotype selected population than FOLFOX based on the data indicating that pemetrexed may be a better TS targeted agent than 5-FU. Patients who are homozygous for the TSER\*2 allele (TSER\*2/\*2) will be able to continue in the study and will be randomized. Patients with other TSER genotypes will not be included and will be considered screen fails. The first 8 patients with the TSER\*2/\*2 genotype will be randomized 1:1 to receive treatment with either PEMOX or FOLFOX (4 in each group). Analysis of the objective response rate (ORR) in each treatment arm will occur after the first 8 patients are enrolled. Using the proposed Bayesian design, subsequent patients will be preferentially assigned to the "better performing" treatment arm based on continuous real-time reassessments of ORR results.