Inclusion Criteria:

- R0 resection (no microscopic residual) of adenocarcinoma of stomach or
gastroesophageal (GE) junction, prior to starting chemotherapy and radiation

- Tumor must not extend more than 2 cm along the esophagus; bulk of the tumor must be
in the stomach.

- Adequate pre-operative cross-sectional imaging (computed tomography [CT] or magnetic
resonance imaging [MRI])

- International Union Against Cancer (UICC)/American Joint Committee on Cancer (AJCC)
Stage IB - IV, excluding patients with metastatic disease (T1N1, T2N0 to T4N1, N2,
and any T, N3). T2N0 eligible only if disease extends beyond muscularis propria.

- No previous abdominal radiotherapy or contraindication to radiotherapy

- Eastern Cooperative Oncology Group (ECOG) performance status < 2

- Adequate major organ function

- Nutritional intake of at least 1500 calories per day at nutrition assessment

- Treatment started within 20-90 days post-op of surgery date.

- Informed consent

Exclusion Criteria:

- Less than 70 years of age