Background: The standard of care for locally advanced esophageal adenocarcinoma(LA-EAC) is concurrent chemoradiation (CRT) followed by esophagectomy. Approximately 30% of patients (pts) achieve complete pathologic response (pCR) with this approach. The risk of relapse in the remaining 70% of pts is high, with 1-yr relapse free survival (RFS) of 50%. No adjuvant therapies have been shown to improve survival. Immune checkpoint inhibitors have activity in metastatic PD-L1 positive EAC. Preclinical studies have shown upregulation of PD-1 pathway with radiation +/- chemotherapy. Methods: We conducted a phase II study evaluating safety and efficacy of durvalumab (durva), a monoclonal antibody against PD-L1, in pts with LA-EAC and GE junction (GEJ) adenocarcinoma who do not achieve pCR after neoadjuvant CRT and R0 resection. Pts received durva 1500mg IV every 4 weeks for up to 1 yr after surgery. Primary objective was 1-yr RFS. Secondary objectives were incidence and severity of treatment related adverse events (AEs). Results: Twenty-four pts were enrolled from Apr 2016 to Jan 2018 (median age: 60yrs (range, 43-74)). Fourteen pts had GEJ adenocarcinoma and 10 had distal EAC. Eighteen received carboplatin/paclitaxel and six received cisplatin/5-FU concurrently with 50-50.4Gy radiation. Nineteen pts (79%) had positive lymph nodes at the time of surgery after neoadjuvant CRT, including three (12.5%) with N3, nine (37.5%) with N2, and seven (29%) with N1 disease. Among N0 pts, two had T3N0, one had T2N0, and two had T1N0 disease. At median follow-up of 11.7 mo (range 1.7-23.9 mo), seven pts (29%) have relapsed (five alive, two died); 17(67%) are disease free (six on treatment, seven completed treatment, three off-treatment); 1-yr and projected 26 mo RFS are 78.6% and 62.9%, respectively. Five pts (20.8%) developed grade 3 AEs: diarrhea (n = 1), hepatitis (n = 1), encephalopathy (n = 1), hyperglycemia (n = 1), hypoglycemia (n = 1). Most common grade 1 and 2 AEs were fatigue (33.3%), nausea (25.0%), and cough (20.8%). Conclusions: Adjuvant durva in pts with residual disease following trimodality therapy for EAC and GEJ adenocarcinoma is safe and feasible with 1-yr RFS of 78.6% compared to historical rate of 50%. Clinical trial information: NCT02639065