The relationships between ABO blood groups and risk of site-specific cancers have been studied since the 1960’s [1]. Previous epidemiological investigations supporting the relationship between ABO blood group and cancer risk have been consistently observed mostly for gastric and pancreatic cancer [2], [3] and [4]. Associations with other cancer sites have been mostly conflicting. The inconsistencies in previous cancer results could possibly be attributed to poor study design that included inappropriate control selection, residual confounding from population heterogeneity, as well as low statistical power. Also, studies that investigated multiple cancer sites [5] present another important challenge of not accounting for both prior knowledge and the number of comparisons made.
Recent meta-analyses of ABO-cancer associations, although was adequately powered was unable to account for other aforementioned pitfalls [6], [7] and [8]. Therefore, in the current study, we investigated the association between ABO blood group and site-specific cancer risk at 45 anatomical sites within a large, well-enumerated cohort of blood donors from the Scandinavian donations and transfusions-2 (SCANDAT2) database, validated our results with previous publications and accounted for multiple testing using false discovery rate (FDR) approach.