All human beings are exposed to the influence of ionizing radiation from 
natural, medical and other artificial sources. Therefore, the influence of 
radiation as a risk factor for cancer development has been among the most 
studied external factors over the last 6 decades, particularly with respect to 
radiosensitive tissues and organs. It has been known that female breast tissue 
is highly sensitive to the carcinogenic effects of radiation, particularly when 
exposure takes place at younger age. All women are exposed to low doses of 
radiation for several common reasons (kind of occupation, medical diagnostic 
procedures, residence background radiation) whose effects on breast cancer 
development cannot be documented, and thus it is believed that ionizing 
radiation is not primary or major risk factor leading to development of breast 
cancer. Radiobiological studies revealed a specific event caused by radiation 
through recognition of the critical target in radiation-induced carcinogenesis. 
Accordingly, mutagenic and carcinogenic effects of ionizing radiation are 
evidenced both in vitro and in vivo, although the incidence of radiation-induced 
cancers is low. The highest risk of radiation- induced breast cancer is 
evidenced in the sub-population of female patients who have undergone 
radiotherapy for either malignant or non-malignant diseases, including benign 
breast diseases in their childhood or young age. Therefore, as a means of 
prevention in this group of population, indications for application of ionizing 
radiation, both diagnostic and therapeutic, should be highly selective, meaning 
that radiation should be applied only if the possible benefit outweighs the 
risk.