1. Required Tumor Parameters

1.1 Patients must have histologically diagnosed adenocarcinoma of the stomach or gastroesophageal junction. Adenocarcinomas of the esophagus that are not involving the gastroesophageal junction are not eligible.

1.2 Patients must have had en bloc resection of all known tumor. The surgical resection must have been done with a curative intent.

1.3 Patients must have tumor extension beyond muscularis propria and/or nodal involvement without evidence of M1 disease.
* Patients can have stages IB if there is evidence of either node-positive (N1) disease or tumor extension beyond the muscularis propria (i.e., T1, N1, M0 patients are eligible but patients with T2, N0, M0 are allowed only if there is extension beyond the muscularis propria).
* Patients can have stages II, IIIA, IIIB or stage IV with M0 (i.e., T4N2M0).
* Stages 0, IA, or any stage with M1 are not allowed. (see Appendix I for TNM staging guide).

1.4 Patients with known unresected cancer, recurrent cancer, microscopic evidence of tumor at the distal or proximal line of stomach resection, noncontiguous resection of tumor, or M1 (metastatic) disease are ineligible.
2. Prior Therapy

2.1 No prior therapy (except hormonal or biologic) for other malignancies is allowed except for adequately treated basal cell or squamous cell skin cancer, noninvasive carcinoma in situ which has been fully resected, or other cancer for which the patient has been disease free for five years.

2.2 Patients who have had any previous chemotherapy or radiotherapy are ineligible.
3. Patient Characteristics

3.1 Patients must have an ECOG (CTC) performance status of 0, 1 or 2.

3.2 Patients are required to have an adequate total caloric intake to allow them to maintain their post-surgical body weight. Patients must have documentation of stable weight (or less than 2 pounds weight loss) for at least one week prior to registration.

3.3 All patients must be evaluated by a radiation oncologist (prior to enrollment) to ensure that the patient is an appropriate candidate for radiation therapy.

3.4 Patients may not have unilateral renal function (only one functioning kidney) as determined by CT scan with contrast, urogram, renal scan, or other study.

3.5 Pregnant or lactating women may not participate. Men and women of reproductive potential may not participate unless they have agreed to use an effective contraceptive method or practice abstinence while in this study.
* The effects of therapeutic radiotherapy are known to be teratogenic.
* The effects of Epirubicin, Cisplatin, and 5-FU on a developing human fetus at the recommended therapeutic dose are less well known.
* For this reason and because DNA alkylating agents are known to be teratogenic, women of childbearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control) prior to study entry and for the duration of study participation.
* Should a woman become pregnant or suspect she is pregnant while participating on this study, she should inform her treating physician immediately. Because the risk of toxicity in nursing infants secondary to Epirubicin, Cisplatin, and 5-FU treatment of the mother is unknown but may be harmful, breastfeeding should be discontinued.

3.6 Patients with any of the following cardiac conditions are ineligible:
* Uncontrolled high blood pressure
* Unstable angina
* Symptomatic congestive heart failure
* Myocardial infarction \< 6 months prior to registration
* Serious uncontrolled cardiac arrhythmia
* New York Heart Association classification III or IV.

3.7 No uncontrolled serious medical or psychiatric illness which would prevent compliance with treatment or adequate informed consent.

3.8 Patients with active infectious process are ineligible.

3.9 Patients with grade 2 or greater peripheral neuropathy at baseline are ineligible.
4. Required Initial Laboratory Values:

* Granulocytes ≥ 1,500/μl
* Platelet count ≥ 100,000/μl
* Creatinine ≤ 1.5 mg/dl
* Bilirubin ≤ 2.0 mg/dl
* AST ≤ 3x upper limits of normal