Low-Dose Aspirin Therapy Does not Increase the Severity of Acute Radiation Proctitis

BACKGROUND: Although anticoagulation therapy is commonly used in the prostate cancer population, there are only a few studies about the correlation between radiation proctitis and anticoagulation therapy. The purpose of the present study was to determine whether low-dose aspirin increases the severity of acute radiation proctitis in an experimental animal model. METHODS: Wistar rats were used in the present study. The rats were administered either aspirin at doses of 5, 10, and 20 mg/kg, or saline, daily before and after irradiation. The rats were irradiated to the rectum as a single fraction of 25 Gy. The rectal mucosal changes of each rat were evaluated macroscopically and pathologically on the tenth day following irradiation. The findings of proctitis were graded from 0 to 4, and then were compared with regard to the status. RESULTS: No apparent correlations were observed between the administration of aspirin and the severity of radiation proctitis in the macroscopic findings and in the morphological mucosal damage in the pathological examination. The proportion of rats with a severe degree of mucosal inflammation was 90.0%, 100.0%, 16.7% and 100.0% at 5 mg/kg, 10 mg/kg, and 20 mg/kg of aspirin, or saline, respectively. The rats receiving aspirin at the dose of 20 mg/kg showed significantly milder inflammation than the other groups (P < 0.05). CONCLUSIONS: In the present study, low-dose aspirin did not increase the severity of acute radiation proctitis. In addition, aspirin might decrease the severity of radiation-induced mucosal inflammation in the rectum.