Effects of hormonotherapy administered after concurrent radiotherapy and Trastuzumab on pulmonary fibrosis

Aim: This study was to investigate whether the use of hormonotherapy after concurrent radiotherapy (RT) and trastuzumab (T) has a contribution to the development of radiation fibrosis in the lungs. Materials and Methods: Seventy Wistar Albino rats were divided into seven groups as follows: Group C: control, Group RT: RT only; Group T: trastuzumab only; Group RT+T+Tam: tamoxifen following concurrent RT and trastuzumab; Group RT+T+Le: letrozole following concurrent RT and trastuzumab; Group RT+T+An: anastrazole following concurrent RT and trastuzumab; Group RT+T+Exe: exemestane following concurrent RT and trastuzumab. Trastuzumab was prepared at an equivalent dose of 6 mg/kg. RT was administered 2 hours after T to the thoracic region at a dose of 12 Gy. Hormonotherapy was initiated one week after RT and administered by oral gavage once daily for 6 months. At the end of 24 weeks, the rats were sacrificed after being sedated with anesthesia. Both lungs were removed en bloc and blocked in paraffin. The level of fibrosis in each cross-section was assessed with the help of a scale. Results: Significant differences were observed between the groups in terms of pulmonary fibrosis scoring. Statistically significant differences were observed when the radiotherapy group was compared to the C, T, T+RT+An, T+RT+Le and T+RT+Exe groups (p<0.05). Significant differences were found between the T+RT+Tam group and the C, T, T+RT+An, T+RT+Le and T+RT+Exe groups (p<0.05). Conclusion: This study showed that the sequential administration of aromatase inhibitors following concurrent thoracic irradiation and T decreases radiation-induced pulmonary fibrosis. However, tamoxifen was found to have an opposite effect.