The purpose of this study is to evaluate the effect of probiotics to improve the intestinal microbiome in malignancy patients who get pelvic/abdominal radiotherapy.

Pelvic/abdominal radiotherapy carries a risk of complications. Acute complications include diarrhea, abdominal pain, inflammatory change in the small intestine. Radiation creates changes in bacterial microbiome, the vascular permeability of the mucosal cells and in intestinal motility. Probiotics were known to improve gastrointestinal function. This is a randomized, double-blind, placebo-controlled study involving 26 patients designed to evaluate the effect of probiotics to change the intestinal microbiome in in patients undergoing concurrent pelvic/abdominal RT.

Inclusion Criteria:

• Patients who current diagnosis of gynecologic cancer or rectal cancer and never previously received radiation therapy and will use for the first time radiotherapy at department of radiation oncology, Seoul National University Hospital.
• ECOG performance status (PS) of 0, 1, or 2.
• signed written informed consent.
• Patients who get pelvic/abdominal radiotherapy.

Exclusion Criteria:

• People who use antibiotics that can affect intestinal microorganism growth within one month before the study.
• Patients who use probiotics within one month before the study.
• Patients received neoadjuvant chemotherapy.
• Acute enteritis symptoms (diarrhea, abdominal pain, nausea, vomiting) for the patient.
• Patients diagnosed with inflammatory bowel disease.
• Patients suspected gastrointestinal infections and other infectious diseases.
• Suspected infections from blood tests : Excessive rise in WBC, ESR, CRP
• Suspected renal insufficiency from blood tests