P09.04 Impact of major oncologic surgery on immune responses in the immediate post-operative setting in oesophageal adenocarcinoma patients; a guide to harnessing the double-edged sword of cancer surgery

BackgroundImmune checkpoint inhibitors (ICIs) are being investigated for their role as an adjunct in the multimodal treatment of oesophageal adenocarcinoma (OAC). The most appropriate time to incorporate ICIs remains unknown. Our study profiles systemic anti-tumour immunity perioperatively to help inform the optimal timing of ICIs into current standards of care for OAC patients.MethodsSystemic immunity in 11 OAC patients was phenotyped prior to oesophagectomy and on post-operative days (POD) 0, 1, 3, 7 and week 6 using flow cytometry. Longitudinal serological profiling was conducted by 54-plex-ELISA. The frequency of circulating lymphocytes, T cells, T helper cells and cytotoxic T lymphocytes was profiled longitudinally. The activation status of T cells was also assessed using CD69, CD27, CD62L and CD45RA as well as the proportion of T cell subsets in circulation, which included: naïve, central memory, effector memory and terminally differentiated effector memory T cells. This study also profiled the longitudinal alteration of immune checkpoint expression on circulating T cells, which included: PD-1, CTLA-4, TIGIT, TIM-3, LAG-3, PD-L1 and PD-L2. Damage-associated molecular patterns (calreticulin, HMGB1 and MIC-A/B) were also assessed.ResultsThe frequency of naïve T cells increased in circulation post-oesophagectomy from POD-0 to POD-7 (p