Background: The standard of care for locally advanced esophageal adenocarcinoma is concurrent chemoradiation (CRT) followed by esophagectomy with lymphadenectomy. Approximately 30% of patients achieve a complete pathologic response (pCR) with this multimodality approach, which has been correlated with improved disease-free survival. The risk of relapse in the remaining 70% of patients who have pathologic evidence of persistent disease in the surgical specimen is extremely high and estimated at 60-70%. Preclinical studies have demonstrated that radiation with or without concurrent chemotherapy upregulates the programmed cell death receptor- 1 (PD-1) pathway by inducing a local inflammatory response, an effect that persists for a number of months after cessation of therapy. Durvalumab is a selective, high affinity, engineered human IgG1 monoclonal antibody that blocks PD-L1 binding to PD-1 and CD80, and has shown activity in metastatic esophageal cancer. The aim of this study is to evaluate efficacy of post-operative durvalumab with respect to decreasing the relapse rate in patients who do not achieve pCR following CRT. Methods: Patients with esophageal adenocarcinoma who have pathologic evidence of persistent disease in the surgical specimen following neoadjuvant concurrent CRT (carboplatin plus paclitaxel or cisplatin plus 5-FU) and R0 resection are eligible for enrollment on this single arm phase II study. Durvalumab 1500mg IV every 4 weeks is started within 1-3 months of surgery and continued for up to 1 year. The primary endpoint is 1-year relapse free survival (RFS). Secondary endpoint is to assess the incidence and severity of overall and treatment related adverse events. Exploratory endpoints include PDL1 expression in tumor and tumor infiltrating lymphocytes, assessment of Immunoscore within the center and invasive margin of the tumor, and the correlation between changes in circulating tumor cell numbers in response to PD-L1 inhibition. The study is currently open to accrual at 5 sites in the Big Ten Cancer Research Consortium and 17 of the planned 23 patients have been enrolled within the past 14 months. Clinical trial information: NCT02639065