DNA double-strand breaks induced by mammographic screening procedures in human mammary epithelial cells

International audiencePurpose: To assess in vitro mammographic radiation-induced DNA damage in mammary epithelial cells from 30 patients with low (LR) or high (HR) family risk of breast cancer. Materials and methods: Spontaneous and radiation-induced DNA double-strand breaks (DSB) were quantifi ed by using immunofl uorescence of the phosphorylated H2AX histone ( γ H2AX) in diff erent conditions of mammography irradiation (2, 4, 2 2 mGy). Results: HR patients showed signifi cantly more spontaneous γ H2AX foci than LR patients ( p 0.014). A signifi cant dose-eff ect was observed, with an exacerbation in HR patients ( p 0.01). The dose repetition (2 2 mGy) provided more induced and more unrepaired DSB than 2 mGy and 4 mGy, and was exacerbated in HR ( p 0.006). Conclusions: This study highlights the existence of DSB induced by mammography and revealed by γ H2AX assay with two major radiobiological eff ects occurring: A low-dose eff ect, and a LOw and Repeated Dose (LORD) eff ect. All these eff ects were exacerbated in HR patients. These fi ndings may lead us to reevaluate the number of views performed in screening using a single view (oblique) in women whose mammographic benefi t has not properly been proved such as HR patients