Diagnostic and therapeutic ionizing radiation and the risk of a first and second primary breast cancer, with special attention for BRCA1 and BRCA2 mutation carriers: a critical review of the literature.

Occurrence of breast cancer is a well-known long-term side effect of ionizing radiation (both diagnostic and therapeutic). The radiation-induced breast cancer risk increases with longer follow-up, higher radiation dose and younger age of exposure. The risk for breast cancer following irradiation for lymphomas is well known. Although data regarding the carcinogenic risk of adjuvant radiotherapy for a primary breast cancer are sparse, an increased risk is suggested with longer follow-up mainly when exposed at younger age. Particularly, patients with a BRCA1/2 mutation might be more sensitive for the deleterious effects of ionizing radiation due to an impaired capacity of repairing double strand DNA breaks. This might have consequences for the use of mammography in breast cancer screening, as well as the choice between breast conserving therapy including radiotherapy and mastectomy at primary breast cancer diagnosis in young BRCA1/2 mutation carriers. Good data regarding this topic, however, are scarce, mainly due to constraints in the design of performed studies. In this review, we will discuss the current literature on the association between ionizing radiation and developing breast cancer, with particular attention to patients with a BRCA1/2 mutation.