While essential recurrence and cancer-specific death risk factors for IBrC include age, menopausal status, nodal involvement, histological grade, and type of received therapy, this analysis presents that the tumor size < 2 cm, Ki67 expression < 20%, luminal-A molecular subtype, and use of effective extra-dose brachytherapy boost could most probably appear as having the most significant positive impact on IBrC disease-free and overall survival and presumably may be considered as independent prognostic factors of breast cancer. This evidence concerns the gene MKI67 and breast cancer.