Clinical Associations with ABO Blood Group and Rhesus Blood Group Status in Patients with Breast Cancer: A Nationwide Retrospective Study of 3,944 Breast Cancer Patients in Turkey.

BACKGROUND The aim of this study was to investigate the association between A, B, O, Rhesus (Rh)-positive and Rh-negative blood groups and breast cancer in a nationwide cohort of 3,944 patients in Turkey. MATERIAL AND METHODS A retrospective study included 3,944 patients diagnosed with breast cancer between 2004 and 2015 and with known blood type. Clinical and demographic patient data included age, sex, body mass index (BMI), menopausal status. The breast tumor type, size, grade, TNM stage, and the presence of lymph node and distant metastases were noted. Histopathology of the breast tumors had included routine detection of human epidermal growth factor receptor 2 (HER2) and estrogen receptor (ER) levels. RESULTS The 3,944 patients with breast cancer were blood group, type A, B, O, and Rh-positive or Rh-negative; the median age was 47.9 years (range, 18.2-89.6 years); 99.5% (3923/3,844) were women, and 0.5% (21/3944) were men. Patients with blood type 0 had a significantly smaller tumor size compared with patients with blood types A or B. There were no significant differences between blood groups and patient age, BMI, menopausal status, tumor histology, ER status, HER2 status, lymph node and distant metastasis. However, there was a significant difference in the prevalence of lobular breast cancer, levels of ER-positive tumor cells, and prevalence of cases with tumor metastases in Rh-positive patients compared with Rh-negative patients. CONCLUSIONS The findings of this retrospective study showed that the type, grade, stage, and hormonal status of breast cancer showed no significant associations with ABO blood grouping.