Histological, immunohistochemical and electron-microscopic evaluation of different radiotherapy doses effects on...

Radiation-related complications occur in the lungs during radiotherapy for intrathoracic tumors. Lung damage caused by radiation in the long term varies depending on the radiation dose received. The incidence of pulmonary toxicity has decreased with the advancement of radiotherapy techniques such as intensity-modulated RT (IMRT) and image-guided RT (IGRT). This study aimed to examine the damage caused by different radiation doses applied with the IMRT technique, both histochemically and histopathologically, and to emphasize the effect of a low dose (5 Gy).

A total of 24 rats were divided into 4 groups: control (Group 1), 5 Gy (Group 2), 10 Gy (Group 3), and 20 Gy (Group 4). Helical IMRT plans were made using tomotherapy to ensure that the thorax received the entire dose designated for each group. The rats in groups 2, 3, and 4 were exposed to radiation doses of 5 Gy, 10 Gy, and 20 Gy, respectively. After 180 days, the morphological and immunohistochemical features and the number of apoptotic cells in the lung tissues were examined using electron microscopy and light microscopy. Morphological, inflammatory (IL-1β, IL-10, and TNF-α), and apoptotic index values were compared statistically.

This study observed that morphological, inflammatory, and apoptotic cell damage in the lungs gradually increased in a dose-dependent manner compared to the control group. However, at the low radiation dose of 5 Gy, the severity of lung damage was relatively less than at the higher doses (10 Gy and 20 Gy).

In conclusion, this study found that the severity of lung damage was less at a low radiation dose (5 Gy) compared to higher doses (10 Gy and 20 Gy). This emphasizes the need to limit the maximum dose and the irradiated volume during thoracic radiotherapy.