Osman Gökhan GÖKDERE, Bahadir ÖNDEŞ, Burhan Hakan KANAT, Feyzi KURT
Eastern Journal of Medicine (EJM) - 2026;31(1):146-151
The Ki-67 proliferation index is an established biomarker reflecting tumor aggressiveness and treatment response in breast cancer. ABO blood group phenotypes have been associated with cancer susceptibility and inflammatory-immunological pathways, yet their potential influence on tumor proliferative behavior remains unclear. This study aimed to investigate the relationship between ABO/Rh blood groups and Ki-67 expression levels in breast cancer. This retrospective study included 189 patients diagnosed with breast malignancy between 2020 and 2024. Ki-67 values were recorded as the percentage of positively stained tumor nuclei. Differences among ABO phenotypes were analyzed using the Kruskal-Wallis test, followed by Dunn post-hoc analysis with Bonferroni correction. Rh groups were compared using the Mann-Whitney U test. All p-values were standardized to three decimal places. A post-hoc power analysis indicated that the sample size (n=189) was adequate to detect a moderate effect size (Cohen's f=0.25) with 80% power at alpha=0.05. The overall mean Ki-67 index was 25.9 +/- 18.7% (median 22%). Ki-67 levels differed across ABO groups with borderline statistical significance (p=0.060). After Bonferroni correction, the largest differences were observed between group O and groups B/AB (adjusted p=0.078 and p=0.083), suggesting a trend toward higher proliferation in non-O phenotypes. No significant association was detected between Rh factor and Ki-67 levels (p=0.810). Although statistical significance was not reached, patients with blood group O demonstrated lower Ki-67 values, whereas B and AB groups tended to exhibit higher proliferation levels. This pattern may indicate a possible biological influence of ABO antigen expression on tumor proliferation. Larger and multicenter studies are warranted to clarify this potential association.
