Long-term outcomes from adding durvalumab to neoadjuvant treatment of operable gastroesophageal cancers: Results from a multicenter study LUD2015-005

398 Background: Phase III studies have shown a survival benefit for the addition of immune checkpoint inhibitors to conventional chemotherapy for patients with gastroesophageal cancer (GEC). Large scale studies of chemoimmunotherapy prior to and after surgery are under way. We sought to characterise the effects of the PDL1 inhibitor durvalumab (D) with standard neo-adjuvant chemo(radio)therapy regimens in an open label phase I/II study in patients (pts) with operable GEC (LUD2015-005, NCT02735239, EudraCT 2015-005298-19). Methods: In pts identified as suitable for potentially curative surgery we gave D (750mg q2w) alongside their standard treatment. Pts had D only at first then Oxaliplatin and Capecitabine (CapOx) q3w or fluorouracil, leucovorin, oxaliplatin and taxotere (FLOT) starting with the third cycle of D. Chemotherapy and further D were given for 6 (CapOx) or 8 (FLOT) weeks before pts had surgery and for up to 12 further infusions of D after operation. Patients on FLOT could also have more chemotherapy. Pts suitable for chemoradiotherapy (CXRT, CROSS regimen) were offered two cycles of D before starting their treatment, and were able to have up to 12 further cycles after recovering from surgery. Participants were followed for toxicity, response and survival from the time of study enrolment until death, for 3 years or until June 2022 when the study ended. Results: 11 pts received D-CapOx, 9 D-FLOT and 15 D-CXRT. All were evaluable for safety and efficacy. Treatment side effects were as expected for the agents used with diarrhoea, nausea and fatigue the most commonly reported and no new safety signals. 156 of 160 planned pre-op D doses were given. Only 2 out of 35 patients did not have surgery, both due to progressive disease on D-CXRT. 23 of the 33 patients having surgery had post-operative treatment. Amongst 33 evaluable pts 2 (5.7%) and 6 (17.1%) had complete or partial pre-op responses (RECIST) and 3 (8.6%) progression prior to surgery. Tumor regression at surgery (Mandard 1-3) occurred in 24/33 pts. Median recurrence free survival was 25.4 months (mo) (D-CapOx), 32.0 mo (D-FLOT) and not reached (D-CXRT). 2 year survival was 81.8%, 77.8% and 77.8% respectively in the 3 arms. Conclusions: Adding D to standard neo-adjuvant regimens for GEC is well tolerated. Survival times and response rates exceeded those expected for the regimens used (2 year survivals with FLOT 68% and CROSS 67%) in this non-randomised multi-centre trial. Clinical trial information: NCT02735239 .