Breast cancer is a solid malignant tumor. In the early stages, these tumors are localized in the mammary gland. However, tumor growth in the later stages may invade into the surrounding tissues and spread to the distant sites and organs. The aim of this study was to determine the chemosensitivity of breast cancer cells, with primary or acquired radiation resistances. Therefore, T47D parental (T47D PAR) cells, T47D invasive (T47D INV) cells and T47D radioresistant (T47D RR) cells were investigated for differences in their responses to chemotherapeutics.