Application of Recombinant Human Superoxide Dismutase in Radical Concurrent Chemoradiotherapy for Cervical Cancer to Prevent and Treat Radiation-induced Acute Rectal Injury: A Multi-center, Randomized, Open-label, Prospective Trial

Purpose To evaluate the efficacy of recombinant human superoxide dismutase (rhSOD) enemas in radiation-induced acute rectal injury (RARI) in patients with locally advanced cervical cancer. Methods In this phase III, randomized, open-label trial (NCT04819685) conducted across 14 medical centers in China from June 2021 to August 2023, all patients received concurrent chemoradiotherapy (CCRT). The experimental group was treated with a rhSOD enema during chemoradiotherapy, and the control group had no enema. The Common Terminology Criteria for Adverse Events (version 5.0) was used to evaluate radiotherapy-induced side effects. Endoscopic appearance was assessed using the Vienna Rectoscopy Score. The primary endpoint in the acute phase was the occurrence rate and duration of grade ≥1 (≥G1) diarrhea during CCRT. Secondary endpoints included the occurrence rate and duration of ≥G2 and ≥G3 diarrhea; ≥G1 and ≥G2 diarrhea lasting at least 3 days; and damage to the rectal mucosa due to radiotherapy measured by endoscopy. Results Two-hundred-and-eighty-three patients were randomly divided into the experimental (n = 141) or control group (n = 140). The mean number of ≥G1 and ≥G2 diarrhea days were significantly lower in the experimental group than in the control group (3.5 and 0.8 days vs. 14.8 and 4.5 days, respectively; P<0.001). The incidence of ≥G2 diarrhea decreased from 53.6% to 24.1% when rhSOD enemas were used. Use of antidiarrheals was lower in the experimental group (36.2% vs. 55.7%, P<0.001). Three patients felt intolerable or abdominal pain following rhSOD enema. RARI grades in the experimental group tended to be lower than those in the control group (P=0.061). Logistic regression analysis revealed that rhSOD enema was associated with a lower occurrence rate of ≥G1/2 diarrhea for at least 3 days (P<0.001). Conclusion The results of this study suggest that rhSOD enema is safe and significantly reduces the incidence, severity, and duration of RARI, protecting the rectal mucosa.