A Study of Durvalumab (MEDI4736) in Esophageal Cancer

Inclusion Criteria: Subject must meet all of the following applicable inclusion criteria to participate in this study: * Written informed consent and HIPAA authorization for release of protected health information obtained from the subject prior to performing any protocol-related procedures, including screening evaluations. NOTE: HIPAA authorization may be included in the informed consent or obtained separately. * Age ≥ 18 years at the time of consent. * ECOG Performance Status of 0-1 within 28 days prior to registration for protocol therapy. * Females of childbearing potential and males must be willing to use two effective methods of contraception (see the protocol) from the time consent is signed until 3 months after treatment discontinuation. * Females of childbearing potential must have a negative serum pregnancy test within 14 days prior to registration for protocol therapy. NOTE: Female subjects are considered of child bearing potential unless they are surgically sterile (they have undergone a hysterectomy, bilateral tubal ligation, or bilateral oophorectomy) or they are ≥60 years old and naturally postmenopausal for at least 12 consecutive months. See the protocol. * Histological evidence of persistent residual esophageal adenocarcinoma including gastroesophageal junction adenocarcinoma following definitive concurrent chemoradiotherapy (carboplatin and paclitaxel or cisplatin and 5-FU) in the surgical sample (esophagus or lymph node or both) obtained at the time of esophagectomy. NOTE: Persistent residual disease is defined as follows (modified from College of American Pathologists Guidelines): * No residual tumor (Grade 0, complete response, 0% tumor). This group will not be included in this study. * Marked response (Grade 1, 0-\<10% residual tumor) * Moderate response (Grade 2, 10-50% residual tumor) * No definite response (Grade 3, \>50% residual tumor) * Minimum of 1 month and maximum of 3 months from surgical resection with no evidence of disease progression at the time of enrollment. * Must have adequately recovered from surgery as judged by the treating investigator. * Subject is willing and able to comply with the protocol for the duration of the study including undergoing treatment and scheduled visits and examinations including follow up. Exclusion Criteria: Subjects meeting any of the criteria below may not participate in the study: * Prior therapy with a PD-1, PD-L1, or CTLA-4 inhibitor or cancer-specific vaccine therapy. * Evidence of active autoimmune disease requiring systemic treatment within preceding 3 months or a documented history of clinically severe autoimmune disease, or a syndrome that requires systemic steroids or immunosuppressive agents. Exceptions to this rule include vitiligo, resolved childhood asthma/atopy, requirement of intermittent bronchodilators or local steroid injections, hypothyroidism stable on hormone replacement, psoriasis not requiring systemic treatment (within the past 2 years), Graves's disease and Sjogren's syndrome. * Prior malignancy is not allowed except for adequately treated basal cell or squamous cell skin cancer, in situ cervical cancer, Gleason score ≤ 7 prostate cancers, or other cancer for which the subject has been disease-free for at least 3 years. * Active or prior documented inflammatory bowel disease (e.g. Crohn's disease, ulcerative colitis). * Presence of interstitial lung disease or history of pneumonitis requiring treatment with corticosteroids. * Patients with diagnosis of primary immunodeficiency. * Patients receiving chronic systemic corticosteroid therapy or other immunosuppressive therapy within 28 days prior to registration for protocol therapy. Exceptions include intranasal and inhaled corticosteroids or systemic corticosteroids at physiological doses, which are not to exceed 10 mg/day of prednisone, or an equivalent corticosteroid. * History of allogeneic organ or stem cell transplant. * Receipt of live attenuated vaccine within 30 days prior to registration for protocol therapy. * Mean QT interval corrected for heart rate (QTc) \> 470 msec calculated from 3 ECGs by Bazett's Correction. * Ventricular arrhythmias requiring medication(s). * Uncontrolled intercurrent illness including, but not limited to, symptomatic congestive heart failure, uncontrolled hypertension, unstable angina pectoris, cardiac arrhythmia, active peptic ulcer disease or gastritis, or active bleeding diatheses. * History of psychiatric illness/social situations that would limit compliance with study requirements or compromise the ability of the subject to give written informed consent. * Known HIV infection or chronic hepatitis B or C. * Known history of previous clinical diagnosis of tuberculosis. * Clinically significant infections as judged by the treating investigator. Clinically significant is defined as an active infection requiring IV antibiotics. * Because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother, breastfeeding should be discontinued. In addition, breast milk cannot be stored for future use while the mother is being treated on study. * Treatment with any investigational agent within 28 days prior to registration for protocol therapy. * History of hypersensitivity to durvalumab or any excipient. * Any condition that, in the opinion of the investigator, would interfere with evaluation of study treatment or interpretation of patient safety or study results. * Previous enrollment in the present study.