ABO blood group and risk of epithelial ovarian cancer within the Ovarian Cancer Association

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" There are two important limitations in the current study. First, controls in the UKG study were not selected at the same time as the cases and may not represent the population that gave rise to the cases. However, in a sensitivity analysis excluding the UKG study populations, the association with the A blood group was largely unchanged (Supplemental Table 4), suggesting that the UKG controls are not a large source of bias. Second, the current study had limited power for the analysis of subgroups, such as potential differences by histologic type, particularly for the less common types, such as clear cell. However, although not statistically significant within all groups, the results were largely consistent among the three most common histologic types (serous, endometrioid, and mucinous). Further, with 5,233 cases and 6,838 controls, this is the largest study of the association between ABO blood group and ovarian cancer to date, with 80% power to detect a relative risk of 1.17 for the AB blood group, indicating that we had adequate power to detect modest associations with even the rarest blood group. Further, this study improves upon previous studies by using appropriate control groups as well as genotype-derived blood groups, which are less likely to suffer from misclassification compared to self-reported blood type. Additionally, the use of genotype-derived blood groups allowed a more detailed investigation of diplotypes rather than the simple blood groups previously investigated."

In summary, our findings for blood group are consistent with previous findings of increased ovarian cancer risk with blood group A. Although potentially due to chance, the finding that this association is limited to the A1/O diplotype should be confirmed in additional studies. Given that the A blood type is associated with a modest increase in ovarian cancer risk, further research into the biological mechanisms linking blood group with carcinogenesis is warranted.