Inclusion Criteria:

• Histological confirmation of node positive (any T stage N1-3) proximal esophageal, distal esophagus or gastroesophageal (GE) junction adenocarcinoma (Siewert I, II, or III) after completing preoperative chemoradiation and surgery. Supporting pathology report sufficient for registration. Available tumor tissue from endoscopic biopsies prior to preoperative chemo/RT, and tumor from surgical specimens will be submitted to the sponsor, but are not required prior to registration. Note: if tissue is depleted, patient will still be eligible after discussion with the physician.
• Imaging (CT or MRI) ≤ 28 days of study registration negative for disease recurrence
• ECOG Performance Status (PS) 0 or 1
• The following laboratory values obtained ≤ 28days prior to randomization
  • Absolute neutrophil count (ANC) ≥1500/mm3
  • Platelet count ≥100,000/mm3
  • Total bilirubin ≤1.5 x the upper limits of normal (ULN)
  • Alanine aminotransferase (ALT) and aspartate amino-transferease (AST) ≤ 2.5 x ULN (≤ 5 x ULN for subjects with liver involvement of their cancer)
  • Alkaline phosphastase limit ≤ 2.5 x ULN (≤ 5 x ULN for subjects with liver involvement of their cancer)
  • Lipase ≤ 1.5 x the ULN
  • Serum creatinine ≤ 1.5 x the ULN
  • INR/PTT ≤1.5xULN. Note-Subjects who are therapeutically treated with an agent such as warfarin or heparin will be allowed to participate provided that their medication dose and INR/PTT are stable. Close monitoring (day 1 of each cycle) is mandatory. If either of these values is above the therapeutic range, the doses should be modified and the assessments should be repeated weekly until they are stable
• Negative pregnancy test done ≤7 days prior to registration, for women of childbearing potential only
• Willing to return to enrolling institution for follow-up (during the Active Monitoring Phase of the study)
• Able to swallow and retain oral medications and begin therapy within 6 to 12 weeks post-surgery
• Provide blood samples for the mandatory correlative research purposes (see sections 6.12 and 14.0)

Exclusion Criteria:

• Presence of metastatic or recurrent disease
• R1 or R2 resection
• Patients who have not recovered from serious adverse events (as determined by treating MD) related to surgery
• Uncontrolled hypertension (systolic pressure >140 mm Hg or diastolic pressure > 90 mm Hg on repeated measurement) despite optimal medical management per physician discretion
• Active or clinically significant cardiac disease including:
  • Congestive heart failure - New York Heart Association (NYHA) > Class II.
  • Active coronary artery disease
  • Cardiac arrhythmias requiring anti-arrhythmic therapy other than beta blockers or digoxin
  • Unstable angina (anginal symptoms at rest), new-onset angina <3 months before randomization, or myocardial infarction within 6 months before randomization.
• Evidence or history of bleeding diathesis or coagulopathy
• Any hemorrhage or bleeding event ≥ NCI CTCAE Version 4 Grade 3 ≤ 4 weeks prior to registration
• Prior cancers < 3 years, with the exception of in-situ cervical cancer, low grade prostate cancer and basal or squamous cell skin cancers.
• Subjects with thrombotic, embolic, venous, or arterial events, such as cerebrovascular accident (including transient ischemic attacks) deep vein thrombosis or pulmonary embolism ≤ 6 months prior to registration
• Receiving any medications or substances that are strong or moderate inhibitors of CYP3A4
• Use of the following strong or moderate inhibitors are prohibited < 7 days prior to registration
• Receiving any medications or substances that are inducers of CYP3A4