The Effects of Hormonotherapy Following Concomitant Use of Trastuzumab and Radiation Therapy on Late Skin Toxicity

To investigate whether hormonotherapy followed by concomitant use of trastuzumab (T) and radiation therapy (RT) contributes to the development of radiation-induced skin fibrosis. 70 healthy female rats divided into seven groups: Control group (C) underwent no procedure. RT group underwent thoracic radiation (TR). T group was administered T. T+RT+Tx group was administered concomitant T and TR, followed by tamoxifen. T+RT+Le group was administered concomitant T and TR, followed by letrozole. T+RT+An group was administered concomitant T and TR, followed by anastrazole. T+RT+Ex group was administered concomitant T and TR, followed by exemestane. Trastuzumab was administered in 6 mg/kg. TR was performed two hours after T administration. Hormonotherapy was given at one week following RT. Rats were sacrificed at 24 weeks. Skin was scored in histopathological examination. Skin inflammation was most commonly seen in the RI, T+RT+Tx and T+RT+Le group. Skin fibrosis was present in all subjects exposed to RT. Control group, T and T+RT+Ex group had the lowest vascular damage scores, while RI, T+RT+Tx and T+RT+Le had the highest scores. The RI, T+RT+Tx and T+RT+Le group had the highest muscular fibrosis scores. Muscular fibrosis was lesser in T+RT+An and T+RT+Ex group. The rate of vascular damage in muscular tissue was the highest in RT, T+RT+Tx and T+RT+Le group. No vascular damage was observed in T and T+RT+Ex group. Our study results suggested that tamoxifen and letrozole following concomitant use of T and RI increased skin fibrosis, while anastrazole and exemestane reduced radiation-induced skin fibrosis.