LAUSR

47Background: Several studies report dense infiltration of tumour-infiltrating T cells and natural killer cells to be associated with an improved prognosis in colorectal cancer (CRC); but whether these associations differ by tumour location remain unknown. This study investigated the prognostic impact of immune cell infiltration in CRC, with particular reference to the anatomical subsite of the primary tumour. Methods: Immunohistochemical expression of CD3, CD8, FoxP3, and CD56 was analysed in tissue microarrays with tumours from 557 incident CRC cases from a prospective population-based cohort. Kaplan-Meier and Cox regression analyses were applied to determine the impact of biomarker expression on 5-year overall survival (OS), in the entire cohort and in subgroup analysis of right colon, left colon, and rectum. Results: In the entire cohort, dense infiltration of all the investigated immune cells correlated significantly with an improved 5-year OS in both univariable and multivariable analysis, adjusted ...