e14527 Background: Immune suppressive treatment is associated with an increased cancer risk due to its negative impact on immunosurveillance. We analyzed the association of immune suppressive treatment with the inflammatory tumor microenvironment and systemic inflammation parameters in patients with solid cancers after lung transplantation. Methods: Systemic inflammation was measured by neutrophil-to-lymphocyte ratio (NLR), leucocyte-to-lymphocyte ratio (LLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR) and CRP/albumin ratio (CRP/Alb) and analyzed at time of lung transplantation and time of tumor diagnosis. In tumor samples, the expression of tumor infiltrating lymphocytes (TIL) including CD3, CD8, CD45RO and PD-L1 using the Ventana Benchmark Ultra system for immunohistochemistry were investigated. Automated tissue analyses were performed for CD3, CD8 and CD45RO TIL (Definiens software). PD-L1 expression was determined by using the combined positive score (CPS). Results: 28 patients with cancer (10 lung cancer, 4 colorectal cancer, 2 renal cell carcinoma, 2 gastric cancer, 2 pancreatic cancer, 2 head&neck tumor, and others) were included in the study. Median time from transplantation to cancer diagnosis was 45 months (range 29-61). 57% (16/28) experienced a period of transplant rejection between transplantation and tumor diagnosis. Therefore, 25% (7/28) of the patients received intensified immunosuppression up to 8 weeks before tumor diagnosis. Median density of CD3+TIL was 5742 cells/ mm2 (range 3,203-8,429), median density of CD8+TIL was 6,363 cells/ mm2 (range 3,643-8,190), median density of CD45RO TIL was 72 cells/ mm2 (range 4-635) and median expression of PD-L1 was 60 (range 5-100) in tumor samples. No statistically significant changes in systemic inflammation were observed from time of transplantation to time of tumor diagnosis (p>0.05; Wilcoxon Signed-Rank Test). Furthermore, a history of transplant rejection before tumor diagnosis was not statistically significant associated with changes in TIL densities or systemic inflammation parameters (p>0.05; Mann Whitney U test). Conclusions: An activated local inflammatory tumor microenvironment as well as stable systemic inflammation characteristics were observed in our cohort. These results support the further development of immunotherapy as treatment approach also in cancer patients under immunosuppression after lung transplantation.[Table: see text]