Abstract Background. The neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) are established markers of systemic inflammation, and they are believed to have prognostic value in various diseases including many common cancers. These indicators of the cellular-mediated inflammatory response are easily obtained from patient blood samples and hold promise as simple and inexpensive tools for risk stratification. Methods. In the present study, 4509 patients spanning multiple cancer types (breast N=979; colorectal N=1024; esophageal N=594; hepatocellular N=287; melanoma N=349 and pancreatic N=1276) treated at Moffitt Cancer Center and with valid hematology lab values, demographic information, clinical disease characteristics, and outcome data were identified. We compared marker counts and ratios across all cancer types to identify disease-specific patterns in pre-treatment host immune response and evaluated the similarities with other established measures of disease-specific immunogenicity. An initial evaluation of the association between pre-treatment NLR, PLR (and corresponding absolute counts of lymphocytes (L), neutrophils (N) and platelets (P)) and disease-specific survival was conducted, controlling for age, sex, race, disease stage, treatment modality, and additionally for primary site and histological and molecular subtypes as appropriate. Results. Mean levels of N, L, P, NLR, and PLR all demonstrated significant differences across cancer types. Pre-treatment NLR was significantly associated with disease-specific death in four of our six cancer sites (colorectal: hazard ratio (HR) = 1.47, 95% confidence interval (CI) = 1.21-1.79; esophageal: HR = 1.38, 95% CI = 1.05-1.82; melanoma: HR = 1.87, 95% CI = 1.18-2.95; pancreatic: HR = 1.69, 95% CI = 1.43-1.99). Pre-treatment PLR was significantly associated with disease-specific death in two sites (colorectal: HR = 1.34, 95% CI = 1.10-1.64; pancreatic: HR = 1.53, 95% CI = 1.30-1.79). This suggests that the utilization of markers of the cellular-mediated inflammatory response for clinical prognosis and decision-making may require disease-specific risk classification criteria. Citation Format: Rachel Howard, Kathleen Egan, Peter Kanetsky. Pretreatment markers of cellular-mediated inflammation and association with survival vary significantly among cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4206.