Our study is considered a continuing effort in radiation therapy treatment of breast cancer. It is concerned a comparison study between the effect of hyperfractionation radiotherapy (a short term course) and hypofractionation radiotherapy (a long term course) of treatment photon doses on breast cancer cells. The comparison is done with refereeing to normal breast tissue measurements using flow cytometric analysis of DNA ploidy studies. Our samples are extracted from normal benign tumors (non-irradiated) and cancer cells in patients pre-irradiated to VARIAN LINAC of 6 MV photon energy at Radiology Department, NCI. S-phase is extracted from flow cytometric analysis that presents a sophisticated comprehension on the rate of growth of breast tumor cells. It is showed a low S-phase fraction less than 7 % in hyperfractionation radiotherapy, however in hypofractionation radiotherapy showed a high S-phase fraction great than 10%. Accordingly, our study reveals the importance of hyperfractionation radiotherapy for breast cancer treatment, its capabilities to kill larger DNA of tumor cells and restrict its populations.