Risk factors for breast cancer: is ionizing radiation among them?

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.