Impact of Probiotic Therapy on Radiation Associated Gastrointestinal Adverse Effects in Patients Undergoing Pelvic Irradiation: A Randomised Clinical Trial

Abstract

Background: Pelvic radiotherapy is an essential component of treatment for gynecological malignancies; however, radiation-induced gastrointestinal toxicity remains a common adverse effect affecting treatment tolerance and quality of life. Radiation-induced intestinal injury is associated with mucosal inflammation, barrier disruption, and alterations in gut microbiota. Probiotics have shown potential in maintaining intestinal homeostasis and reducing radiation-associated gastrointestinal complications.

Aim: To evaluate the efficacy of probiotic supplementation in reducing acute radiation-induced gastrointestinal toxicity in patients receiving pelvic radiotherapy for gynecological malignancies.

Materials and Methods: This prospective randomized controlled study was conducted from September 2024 to February 2026 and included 50 patients undergoing pelvic radiotherapy. Patients were randomized into two groups: Group A (n=25) received oral probiotic supplementation containing Lactobacillus and Bifidobacterium species, initiated before radiotherapy and continued until completion of treatment; Group B (n=25) received standard supportive care. Gastrointestinal toxicity was assessed weekly including diarrhea severity, abdominal pain, use of antidiarrheal medication.

Results: Baseline demographic, clinical, and treatment-related characteristics were comparable between both groups. The mean daily frequency of loose stools during radiotherapy was lower in the probiotic group compared with controls, although not statistically significant (1.09 ± 0.86 vs 1.45 ± 1.13; p=0.21). Probiotic supplementation significantly reduced loose stool frequency during the 14 days after completion of radiotherapy (0.65 ± 0.49 vs 1.40 ± 1.05; p=0.003). The number of days with more than one loose stool was significantly lower in the probiotic group during radiotherapy (7.97 ± 5.82 vs 15.36 ± 9.04 days; p=0.001) and during post-radiotherapy follow-up (3.64 ± 2.43 vs 6.96 ± 3.72 days; p<0.001). Abdominal pain severity was also significantly reduced among patients receiving probiotics (0.33 ± 0.56 vs 0.84 ± 0.96; p=0.009).

Conclusion: Probiotic supplementation significantly reduces the severity and duration of radiation-induced gastrointestinal symptoms, particularly diarrhea and abdominal pain, in patients undergoing pelvic radiotherapy. Probiotics may serve as a safe, cost-effective supportive intervention to improve treatment tolerance and quality of life. Larger multicenter studies with microbiome analysis and long-term follow-up are required to validate these findings.