Preclinical data indicate that rifaximin could be repurposed as a novel strategy for preventing and reducing the severity of gastrointestinal damage, particularly diarrhea, that results from pelvic irradiation. So, The aim of the work is to investigate the impact of Rifaximin on the incidence and severity of radiotherapy-induced diarrhea in cancer patients undergoing pelvic irradiation with or without chemotherapy.

Inclusion Criteria:

• Individuals who are 18 years of age or older and have been diagnosed with non metastatic pelvic cancers.
• Patients who are undergoing curative intent radiotherapy with or without chemotherapy treatment.

Exclusion Criteria:

• Patients who have a record of intestinal resection in their medical history.
• Patients with a medical background of irritable bowel syndrome.
• Patients with a history of inflammatory bowel disease.
• Patients who regularly take anti-diarrheal medications before commencing radiotherapy.
• Patients experiencing diarrhea at the outset of the study.
• Patients with compromised immune systems, such as those who are HIV positive or using immunosuppressive medications.
• Pregnant or lactating woman.
• Patients allergic to rifamycin.