Study of Pembrolizumab in Locally Advanced Esophageal Adenocarcinoma

Inclusion Criteria: 1. Patients must have histologically or cytologically confirmed esophageal or GEJ adenocarcinoma 2. Clinical tumor stage should be T2 Npositive M0 or T3--T4, Nany, M0 3. Be willing and able to provide written informed consent/assent for the trial 4. Be 18 years of age or older on day of signing informed consent. 5. Be a candidate for surgical resection. 6. Be willing to provide tissue during endoscopic assessment of their tumor. 7. Have a performance status of 0 or 1 on the ECOG Performance Scale. 8. Demonstrate adequate organ function as defined below, all screening labs should be performed within 14 days of treatment initiation. * Absolute neutrophil count (ANC) ≥1,500 /mcL * Platelets≥100,000 / mcL * Hemoglobin ≥9 g/dL or ≥5.6 mmol/L without transfusion within 7 days of assessment * Serum creatinine OR Measured or calculated creatinine clearance ≤1.5 X upper limit of normal (ULN) OR * ≥60 mL/min for subject with creatinine levels \> 1.5 X institutional ULN (Creatinine clearance should be calculated per institutional standard) (GFR can also be used in place of creatinine or CrCl) * Serum total bilirubin ≤ 1.5 X ULN OR * Direct bilirubin ≤ ULN for subjects with total bilirubin levels \> 1.5 ULN * AST (SGOT) and ALT (SGPT) ≤ 2.5 X ULN * Albumin \>2.5 mg/dL * International Normalized Ratio (INR) OR Prothrombin Time (PT) ≤1.5 X ULN unless subject is receiving anticoagulant therapy as long as PT or PTT is within therapeutic range of intended use of anticoagulants * Activated Partial Thromboplastin Time (aPTT) ≤1.5 X ULN unless subject is receiving anticoagulant therapy as long as PT or PTT is within therapeutic range of intended use of anticoagulants 9. Female subject of childbearing potential should have a negative urine or serum pregnancy within 7 days prior to receiving the first dose of study medication. If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required. 10. Female subjects of childbearing potential should be willing to use 2 methods of birth control or be surgically sterile, or abstain from heterosexual activity for the course of the study through 120 days after the last dose of study medication (Reference Section 5.7.2). Subjects of childbearing potential are those who have not been surgically sterilized or have not been free from menses for \> 1 year. 11. Male subjects should agree to use an adequate method of contraception starting with the first dose of study therapy through 120 days after the last dose of study therapy. Exclusion Criteria: 1. Is currently participating and receiving study therapy or has participated in a study of an investigational agent and received study therapy or used an investigational device within 4 weeks of the first dose of treatment. 2. Evidence of metastatic disease. 3. Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy or any other form of immunosuppressive therapy within 7 days prior to the first dose of trial treatment. 4. Has active TB or a history of active TB within 10 years of registration (Bacillus Tuberculosis) 5. Hypersensitivity to pembrolizumab or any of its excipients. 6. Has had a prior anti-cancer treatment, including chemotherapy, radiation, or monoclonal antibody (mAb) for their current diagnosis of esophageal adenocarcinoma. 7. Has a known additional malignancy that is active. Exceptions include basal cell carcinoma of the skin or squamous cell carcinoma of the skin that has undergone potentially curative therapy or in situ cervical cancer. 8. Has a previous invasive malignancy treated with curative intent less than 3 years from time of registration. Exceptions include prostate cancer, basal cell squamous skin cancer, and cervical cancer. 9. Has active autoimmune disease that has required systemic treatment in the past 2 years (i.e. with use of disease modifying agents, corticosteroids or immunosuppressive drugs). Replacement therapy (eg., thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency, etc.) is not considered a form of systemic treatment. 10. Has known history of, or any evidence of active, non-infectious pneumonitis. 11. Has an active infection requiring systemic therapy. 12. Has a history or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the trial, interfere with the subject's participation for the full duration of the trial, or is not in the best interest of the subject to participate, in the opinion of the treating investigator. 13. Has known psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the trial. 14. Is pregnant or breastfeeding, or expecting to conceive or father children within the projected duration of the trial, starting with the pre-screening or screening visit through 120 days after the last dose of trial treatment. 15. Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent. 16. Has a known history of Human Immunodeficiency Virus (HIV) (HIV 1/2 antibodies). 17. Has known active Hepatitis B (e.g., HBsAg reactive) or Hepatitis C (e.g., HCV RNA \[qualitative\] is detected). 18. Has received a live vaccine within 30 days of planned start of study therapy. Note: Seasonal influenza vaccines for injection are generally inactivated flu vaccines and are allowed; however intranasal influenza vaccines (e.g., Flu-Mist®) are live attenuated vaccines, and are not allowed.