TURKISH JOURNAL of ONCOLOGY Effect of Radiotherapy Dose Rates on Early Intestinal Toxicity Dilek ÜNAL, 1 Serhat AYDOĞAN, 2 Arzu TAŞDEMİR, 3 Tuba Dilay ÜNAL, 3 Harun ÇELİK, 1 Hatice KARAMAN, 3 Celalettin EROĞLU, 4 Bünyamin KAPLAN 4 Received: March 3, 2016 Accepted: March 8, 2016 Accessible online at: www.onkder.org 1 Department of Radiation Oncology, Kayseri Training and Research Hospital, Kayseri-Turkey 2 Department of Anesthesiology and Reanimation, Kayseri Training and Research Hospital, Kayseri-Turkey 3 Department of Pathology, Kayseri Training and Research Hospital, Kayseri-Turkey 4 Department of Radiation Oncology, Erciyes University Faculty of Medicine, Kayseri-Turkey OBJECTIVE Te aim of the present study was to investigate early histopathological changes in small intestinal tissue caused by radiotherapy (RT) applications with varying dose rates in rats. METHODS Tirty rats were divided into 3 groups. Te frst and second groups were irradiated at 300 MU/min and 600 MU/min, respectively. Te third was a control group. On day 7 following RT application, small intestine tis- sue samples were obtained. RESULTS Mucosal thickness was signifcantly lower in the 300 MU/min group, compared to the other groups, and thickness was signifcantly lower in the 600 MU/min group, compared to the control group. Villus length was signifcantly decreased in the 300 MU/min group, compared to the other groups, and villus width was signifcantly increased in the control group, compared to the other groups. CONCLUSION RT application with high dose may be less toxic for tissue with high risk for acute toxicity, such as that of the small intestine. Keywords: Radiotherapy dose rate; rat; small intestine; toxicity. Copyright © 2016, Turkish Society for Radiation Oncology Introduction Radiotherapy (RT) is an important cancer treatment option, and is generally used in combination with other treatment alternatives, such as chemotherapy or tumor-removing surgery. Modern technology has al- lowed for the delivery of localized radiation to nearly every part of the body. However, normal tissue toxic- ity remains the most signifcant dose-limiting factor in clinical RT applications.[1] Radiation targets cellular DNA and can produce immediate cell death or loss of ability to sustain cell division.[2] In some cell types, cell death occurs rapidly, within several hours of irradia- tion.[3] Tis type of death, interphase death, is primar- ily limited to thymocytes, lymphocytes, spermatogo- nia, and other cells in rapidly proliferating tissue such Dr. Dilek ÜNAL Kayseri Eğitim ve Araştırma Hastanesi Radyasyon Onkolojisi Kayseri-Turkey E-mail: dilekunaldr@gmail.com Turk J Oncol 2016;31(1):5-9 doi: 10.5505/tjo.2016.1399 ORIGINAL ARTICLE