BackgroundTo compare the severity of radiation-induced lung injury (RILI) after the right lung of SD rats received interstitial brachytherapy and stereotactic radiotherapy (SBRT).MethodsRILI rat model was established using interstitial brachytherapy and SBRT methods, respectively. CT scan was performed to analyze the lung volume and the CT value difference between the left and right lungs in rats. Then the lung tissues were analyzed through H&E staining, peripheral blood was extracted to detect the expression levels of serum inflammatory cytokines, pro-fibrotic cytokines, and fibrotic-inhibiting cytokines by ELISA.ResultsThe difference between right and left lung CT values was significantly elevated in the SBRT group when compared with the control group and the interstitial brachytherapy group (P< 0.05). The IFN-γ expression in the interstitial brachytherapy group was significantly different from that in the SBRT group at week 1, 4, 8 and 16. Besides, the expressions of IL-2, IL-6 and IL-10 in SBRT group were significantly higher than that of interstitial brachytherapy group (P< 0.05). The TGF-β expression in interstitial brachytherapy group reached its peak with the increase of time from week 1 to week 16, and it was significantly lower than SBRT group (P< 0.05). The mortality rate in the SBRT group was 16.7%, which was significantly higher than that in the interstitial brachytherapy group.ConclusionThe treatment method of interstitial brachytherapy is considered as an effective and safe tool by reducing the side effects of radiotherapy and increasing the radiation dose of radiotherapy.