Aromatase inhibitors and radiation-induced lung fibrosis

614 Background: In experimental and clinical trials, tamoxifen (TAM) has been shown to increase radiation-induced lung fibrosis (RILF). Aromatase inhibitors (AI) are superior to TAM in the adjuvant setting, and preclinical data suggest that letrozole (LET) sensitizes breast cancer cells to ionizing radiation. However, poor data are available regarding the toxicity of concurrent use of AI and radiation therapy (RT). In this experimental study, we evaluated whether AI have any impact on the development of RILF in rats. Methods: 60 female wistar- albino rats were divided into 6 groups: control (group A), RT alone (group B), RT + TAM (group C), RT + anastrozole (ANA group D), RT + LET (group E), and RT + exemestane (EXE, group F). RT consisted of 30 Gy in 10 fractions to both lungs with an anterior field at 2-cm depth. Equivalent doses for 60 kg adult dose per day of TAM, ANA, LET, and EXE i.e. 20 mg, 1 mg, 2.5 mg, 25 mg, respectively, were calculated according to the mean weight of rats which was 200 gr and ...