Inclusion Criteria:

- Age > 18 years

- Ability to sign informed consent and understand the nature of a placebo- controlled
trial.

- Ability to complete questionnaire(s) by themselves or with assistance.

- Life expectancy ≥ 6 months.

- Current diagnosis of cancer that supports the use of continuous definitive or
adjuvant external-beam RT to the pelvis to a minimum dose of 4500 cGy delivered with
conventional multi-field photon radiotherapy, 3-D conformal photon radiotherapy or
intensity modulated photon therapy.

- Will receive concurrent administration of chemotherapy (5-FU, capecitabine,
cisplatin, oxaliplatin, carboplatin, and/or mitomycin) during pelvic RT

- The following laboratory values obtained > 28 days prior to registration:

Hemoglobin > 10.0 g/dL WBC > 3,500 Absolute neutrophil count > 1,500 Platelets > 100,000

- ECOG Performance Status (PS) of 0, 1 or 2

- Willing to abstain from ingestion of yogurt products and/or any product containing
probiotics during study drug treatment.

Exclusion Criteria:

- Current or prior metastases beyond regional lymph nodes.

- Undergone abdominal-perineal resection, Hartmann procedure, or other surgical
procedure leaving the patient without a functioning rectum.

- Known allergy to a probiotic preparation.

- Any history of inflammatory bowel disease.

-> grade 3 diarrhea, rectal bleeding, abdominal cramping, or incontinence of stool,
≤7 days prior to registration.

- Any medical condition that may interfere with ability to receive protocol treatment.

- Planned use of leucovorin (because of the risk of secretory diarrhea).

- Split-course RT is planned.

- Prior pelvic RT.

- Proton RT.

- Any of the following:

Pregnant women Nursing women Men or women of childbearing potential who are unwilling to
employ adequate contraception

- Use of probiotics ≤ 2 weeks prior to registration.

- Use of antibiotics ≤ 1 week prior to registration.

- Planned continuous antibiotic treatment during RT.

- History of gastrointestinal or genitourinary obstruction or porphyria.