Since high BARD1/BRCA1 expression predicts poor prognosis in ER+ early breast cancer patients, it is possible that PI3K inhibitors not only help to overcome endocrine resistance, but may also reverse the resistance to DNA-damaging chemotherapy and radiotherapy in ER+ early breast cancer patients that have a 29–45% chance of PIK3CA mutation. This evidence concerns the gene BARD1 and breast cancer.