A new study has reported that blood type does not appear to be linked to breast cancer survival. The study was designed to investigate the associations between blood type, HER2 status, and breast cancer outcomes. Altered glycosylation, a process in which sugar is attached to proteins, has been associated with cancer potential. A change in glycopattern of proteins will trigger a change of function of the proteins. Abnormal glycosylation occurs in essentially all types of human cancer. In the study, relationships of blood types (where expression is due to glycosylation pattern) and HER2/neu (where expression arises due to altered glycosylation) and breast cancer associated hormone receptors (estrogen receptor (ER) and progesterone receptor (PR)) were examined and related to outcomes in breast cancer patients.

The study included 426 women who underwent breast cancer surgery and treatment at the same Cancer Treatment Centers of America medical center during a 10-year period. HER2/neu was overexpressed in under 20% of the study group.

Only tumor size was found to vary significantly according to blood type; women with type A or B were less likely to have tumors over 2 cm compared to women with type AB or O. Women with type B blood were overrepresented in the study group compared to proportion of type Bs in the general population (suggesting that type B women are more likely to develop breast cancer), whereas women with type AB were underrepresented. However, no significant differences were observed in five-year overall and disease-free survival based on blood type, after adjusting for age, disease stage, and treatment with Herceptin (trastuzumab), tamoxifen, or aromatase inhibitors. HER2/neu overexpression was associated with a five-year disease free survival rate of 75% and overall survival of greater than 80% across all blood groups. The authors conclude that no significant differences were found in survival based on blood type. In addition, no correlation was found between HER2/neu, ER or PR status, and blood group.

Please see our article on blood type for more information on blood type, breast cancer risk, and diet.